I've not been able to use any of the example objects to help further. See the FAQ: How to do a minimal reproducible example reprex for beginners. For a problem like this was would help most is a dput() of a json file with two simple records, one which parses and one that doesn't.
The idea is to isolate where the problem is arising: Does the source have poorly json? If fromJSON parses then it is something later in processing that is the difficulty.
Less is more—just the minimum information to illustrate.