Frequent failures uploading to ecloud

Hi, I have an old stock android phone and my shiny, new FP4 with /e/ on it. I’ve set up NextCloud on both, in order to relatively simply sync over some stuff I’d like to keep.

Syncing biggish files seems to be no problem (signal backup, SMS backup, etc), but copying more than one or two files at the same time always fails. If I select 5 photos on the old phone and set them to share via NextCloud and dump them in my Pictures folder on ecloud, I usually get just one, but at least no more than two. Have to manually retry each one (this works, however).

Do other people see this? I realize this is a free service, and the upload/download speed I get is perfectly fine, but it’s a hassle. I haven’t uploaded much from my new phone, but I do see the same (probably) when I tried SeedVault backup, which would invariably fail after backing up a few percent.