HDMI Audio Swapped?

Okay so I am running into the oddest issue I have seen in a while and I cannot figure out for the life of me where the issue is. I have an issue with a stereo audio feed on a program monitor showing as reversed when monitoring directly from a streaming encoder's output. And only on that one send, and it seems to be from a matrix switcher or encoders output which are all HDMI audio driven?

This is a fairly complex setup going on so bear with me,

For video, There is an ATEM Constellation 8K, as well as an Atlona Pro2HD1616M, 16 input by 16 output HDMI/HDbaseT Matrix switcher. All PCs (4 in total) Enter the 16 in by 16 out matrix and can be routed to various destinations. There are 6 links from Matrix outs to Feed ATEM inputs, and all sources work with audio and video going in just fine. HDMI Matrix Output 16 feeds a Projector, HDMI Matrix Output 15 feeds a program monitor. HDMI Matrix Input Source 15 is from a converted SDI to HDMI signal from ATEM ME1 Program out, while HDMI Matrix input 16 is a return from the Encoder (an Extron SMP351)

The Main PC audio out is not via HDMI, but rather from a Decklink output card, that feeds into a DSP Audio Processer for Gain leveling and limiting to the ATEM inputs 1 and 2 TRS jacks. From there the audio gets embedded over the ME1 Program output SDI which feeds back into the HDMI matrix Input 15 (as already mentioned above) which then routes audio to the encoder over HDMI.

I can use this setup to monitor on the program monitor, either the audio/video going out the ATEM pre Extron encoder, as well as post Extron encoder to make sure everything is well in good at various points in the path.

But here is where it gets weird, if I monitor the audio from out of the ATEM before it hits the Extron encoder on the program monitor all is well. Left channel is indeed the left channel and right is the right as I would expect. If I switch the HDMI Matrix Switcher video source on the program monitor to view the Extron encoders output, then the audio channels on the program monitor are swapped? Left plays over right and vice versa?

But the only thing switching in this case is the HDMI matrix sends to that monitor, and all audio at that point is digital over HDMI cables?

If I mute one side coming in and trace the audio all the way through, I can see that left is indeed left on the Extron Encoders web gui page. So in the Extron setup itself, the audio shows as it should, signal is coming on left digital HDMI input (analog inputs are disabled) and shows on the left channel coming in and going out just as expected. After that it is again Digital from the HDMI cable out of the encoder back into the HDMI matrix, which when then switched to the program monitor, shows as audio being reversed? Same program monitor shows everything correctly when switched back to ATEM Program out pre Extron Encoder. If I try to send audio out over the PC HDMI cable instead of the decklink card analog outs, I get the same swapped audio on the output of the Encoder only. Everything going in seems fine every time.

Could this matrix be the issue? It has no web gui to check as it is an older unit that is all RS232 controlled only. I have not found any RS232 commands to swap audio in the manual, there is reset command for it, but I am hesitant to do that yet and erase all the EDIDs stored inside. I may need to call Atlona to see if it is possible to even swap the audio in these matrixes.

I have swapped HDMI cables and still the issue persists. Everything points to the path (HDMI Cable) between encoder and matrix somehow swapping left/right but only for input 16? The Program monitor is a Marshall V-LCD171MD, If I send the same two HDMI Matrix inputs 15 & 16 to the projector, I also get swapped L/R when viewing Input 16, input 15 is fine as always.

I have double checked every cable and routing several times in the audio processor, every setting in every device menu I can think of and everything lines up as it should all the way until the Digital output of the Encoder once it leaves via HDMI. Unplugging the HDMI cable from the Encoder output does kill all audio on the program monitor feed when set to input 16, even when one side is muted. so That has to be the signal source. There are no audio swap option settings in the Extron.

I am not exactly new to this game either, I have been doing AV for over 25 years now, mostly as a commercial and broadcast AV design engineer, I have dealt with some pretty large systems on a very deep level and have never seen this before? I am just dumbfounded on how this is even possible..

Has anyone else seen HDMI L/R audio signals get swapped in the digital domain but only for one specific input?

Edit: A few additional tests I have tried

I swapped the Matrix input 16 into input 15 and the same issue persisted on input 15, so I am fairly certain this is down to the Extron Encoder, to test that theory more, I grabbed a 7" HDMI monitor from a camera rig and plugged it directly into the Extron Encoders HDMI output and monitored from the small 7" Display. Audio is also swapped going into the 7" Display directly from the HDMI out on the Extron? It certainly seems this encoders HDMI output is reversing the audio on the HDMI output. Stream seems fine going out and recording to the internal drive also seems fine. Only the HDMI out is swapped.. so strange Extron...

Edit 2: Just connected the Extron's Analog audio outputs to a recorder and they are also just fine? Only the HDMI audio is showing as swapped..

Edit 3: Ticket submitted to Extron, talking with the support person was interesting to say the least. I told them everything I had tried and they just sat silent for a several seconds trying to process it. We walked through the signal chain and they are stumped for the moment, but they do agree that it seems to be the Extron unit from all of my testing, are going to see what can be done about it. They are going to have engineering take a deeper look after this upcoming weekend's production. This unit was purchased used a few years ago and it seems to have originated from a supplier from Israel. It is now in the states so it has travelled a bit it seems. Curious to see if anyone knows of any reasons why audio might be swapped for different regions? This is something Extron is also investigating. Hoping it is an easy fix and that this does not need to be sent in.