I feel your pain, I tried tons of other solutions before discovering KDE Connect. It works well for my laptop/phone combination, but I'm not surprised if it doesn't work for others, given how horrible each other solution was that I've tried.
edit: I wonder if perhaps some part of your phone hardware overheats after N megabytes because it's not built for constant file transfer, or constant file transfer using these protocols at least? What if you try throttling it on purpose?
I think it is the fault of the network stack of one those two devices, otherwise I can't explain that. Maybe that the devices receive/send data faster than they are able to process. (Is this even possible?)
But I could be awfully wrong
Regarding your edit: That's a good idea, but I never attempted that. I can't test that, because I'm in a Wifi where no device is allowed to talk to another :(
I feel your pain, I tried tons of other solutions before discovering KDE Connect. It works well for my laptop/phone combination, but I'm not surprised if it doesn't work for others, given how horrible each other solution was that I've tried.
edit: I wonder if perhaps some part of your phone hardware overheats after N megabytes because it's not built for constant file transfer, or constant file transfer using these protocols at least? What if you try throttling it on purpose?