DSM920+ won't update anymore

DSM920+ stuck on DSM 7.2.2-72806 Update 5. DSM 7.3.2-86009 Update 4 is available to download. However, I have auto update on for weeks, and I've tried to manually install several times. Screen locks up on clicking install now for \~30 minutes, then just goes back to offering to install/download it again.