de0u The statement "If you've been rooting or otherwise messing with the official releases, we cannot help you with this issue" (especially the word cannot) implied to me that rooting was being blamed for this issue.
I'm really unsure of why rooting the device is considered different than any of the other hundreds of important modifications that can be made to it within the existing operating system. You don't know what apps people have installed, what permissions they've been granted, how all the system settings are configured, etc etc. (Although these are all things I would be more than happy to provide about my setup.)
Regarding the concern about how my device "has been modified in unknown ways" - the ways are certainly not unknown to me, and I'm happy to share exactly what modifications have been made. I simply use Magisk (or specifically this fork that adds GrapheneOS compatibility) to apply Trust User Certs, Block Ads, and (in the past but no longer) MagiskFrida and SafetyNet Fix.
I could believe that MagiskFrida could cause issues around process spawning (and indeed I've reported bugs around that to the module author), but I removed that module as a consequence. The other modules seem completely unrelated to app suspend/resume, and especially do not seem like they would be making persistent modifications to the system that would survive past the ROM being re-flashed.