NOS keeps dropping the data connection from my French SIM in Portugal (One UI 8.5). MEO refuses to connect. What can I do?

Hi,

I have an S24 Ultra with a French sim (one of the major operators in France), One UI 8.5, now roaming in Portugal. Per EU Roaming rules, I should get the same data/calls here in Portugal, as if I were in France. This works most of the time in most countries - however, for some reason, now in Portugal, I keep losing my data connection. When it happens, I can send/receive texts and calls, but nothing else. The connection drops a few times per week, but it is quite annoying as I stop receiving any data calls and messages at all.

I tried forcing one operator (NOS) so as not to get jumps between NOS, MEO and other possible operators. Doesn't solve it.

When data breaks, any of the two below solutions may work, but also may not. In any case, you have to try several times, most times:

1. Go in and out of airplane mode 2. Go back to network selection, scan, and tap "NOS" again. When it fails, it says "can't register on the network, try again later".

I only have 1 active sim, my French physical sim. I've had it for years, usually no issue.

What gives? Is MEO somehow in breach of the EU data roaming rules by trying to curtail my traffic to save on crowded antennas? What are my ways of recourse against something like this? Is there any way to force 24/7 data availability, beyond local esims?

Thank you for any feedback on this *specific* problem!