Issues with rebuilding/upgrading AUR packages
If I cancel the transaction, or the transaction fails, all packages that I previously marked for rebuild (installed but still marked for Build) would become unmarked.
Also, in case of a transaction failure, all packages that were marked for Upgrade would become unmarked and and has to be selected manually. Additionally, for some reason, manually unmarking an AUR package for Upgrade (in case the package can't be built right now or if the installation is not straightforward) would give out an ignoring package upgrade
warning that makes little sense.
As AUR packages can break over time in cases of an update of a crucial system library, I've started to use some utilities, like rebuild-detector, to check whether I need to rebuild some of the foreign packages installed on the system, or purge them, if they're not maintained anymore (neither in official repo nor in AUR).
Haven't checked if this issue has been reported/acknowledged before, but the issue has been there for quite a long while. I didn't really pay too much attention to this as whenever this happens I'd usually just reselect them manually, or restart pamac-manager entirely (if it's mostly about upgrades).