I posted a similar thing...our setup is incredibly similar as well.
Suggestions like read/write access for all users to the network location of
the database, but I'd already checked that...
We've isolated to a particular user that when this person is in the office,
the locking is incredibly frequent, and almost never when he is out of the
office. Database also split FE/BE, and it appears there is a "master form"
with each user having their own "personalised" version of the master form.
I can now see why copying someone else's FE wouldn't have worked as it would
have copied the problem...
We've only got this far because it's been happening for over a year, and the
user's pointed out that it was problematic with one particular person and
they identified it by him being out of the office so I guess I had a
headstart. I can only suggest that you find a way to track who actually had
it locked. It seems somewhat inconsistent in the beginning, and that's
probably because of the randomness of creating the new records (that's what I
think anyway). You may also find in your case that it is one particular
person causing it...
I don't know how to set it so you can have a report of sorts generated, but
maybe someone here can help you in that direction. Good luck.