SQL tag stops execution rate

I have some SQL tags that appear to stop updating.
execution rate is set to 1 min.

There are times that I find it not updating at all. If I go into the tag and turn on the "green dot for UDT change" hit apply then turn it off and apply. It will start updating again.

Any ideas of why it might be doing this and/or suggestions about keeping it consistently updating?

Get a thread dump next time you think one should have executed but hasn't.