I haven't changed anything other than swapping out TM for Borg. The backups still reside on the Synology (Borg is available on SynoCommunity: https://synocommunity.com/package/borgbackup), and I still backup over WiFi. The Vorta (Mac UI for Borg) client and user experience isn't Apple levels of polished like TM, but I've made it work and I'm happy enough with it.

I'm not sure what causes TM to start considering the volume corrupted, because I believe at one point I switched over to a hardwired connection, but still saw a corrupted volume.

I compared that to Borg, which doesn't flinch if you SIGKILL the process mid-backup, and will basically just pick up from where it left off if you start another one. I saw no reason to continue with TM at all.