sorry about the delayed response, I've been a bit busy the last few days. After some finagling with the mechanics it seems like vines are completely blocking all tree growth, something that it definitely wasn't doing back in 1.15.
I would like to point out, this also happens when spreading nylium blocks
It seems logical to assume that this could be resolved by something where villagers of higher tiers can kick lower tier villagers off of their jobsites.
I would like to mention this is still a problem in 1.14.4. It seems that unemployed villagers have first dibs on workstations which messes things up when you're moving a workstation with unemployed villagers present.
Version: vanilla server jar version 1.14.3
Confirmed though the /kill command above can be used to fix it "The easiest way to get rid of Item Frames would be to use '/kill @e[type=ItemFrame]'"
it appears to happen in both old and new worlds.