So sorry to hear Finley didn't like the playpen time. He might adapt better the next time, if there is no health check and weigh at the same time. Pip was a bit like this his first time and spent most of the time hiding or making a squeaking noise, but he did eventually get distracted by finding a pile of food. However I didn't try to handle him or do a health check on that occasion. The next time he was more confident and it was more familiar.
But as you say he may have had a past trauma as well. It would be nice if he could learn to feel safe in a playpen though.