Seems like a “well-known fact” but I don’t have encountered a buggy behaviour yet. Most topics on “PUM bugs” are over 4-5 years old. I only have my OT for 2 months, but PUM’s were the main reason I got one in the first place so I’ve been using these from the beginning in spite of the many “why don’t you use Flex” replies being triggered each time I mention PUM’s in a post. Anyway, each time I have a PUM misbehaving, until now it has always been a lack of understanding on my behalf.
For the record, I don’t use Flex machines for live looping (guitars and bass) because you need to set everything up first. With a PUM I hit a footswitch to start recording next time the pattern loops, and hit it again when I want to stop and start looping the recording next time the pattern loops, regardless of how many bars I recorded. If that is possible with a Flex I’d be happy to learn how!