For example:  If you enter 9,999 in field 20Z and lets say 400,000 in 20AB, PTO fails to see these as numbers, no QBI income is registered, and no error message or diagnostic is generated, which some preparers might assume is due to some limiting factor in the the complex web of limitations on 199A.  However, it's just a software failure, if you remove the commas like 9999 in 20Z and 400000 in 20AB, the correct QBI deduction flows through (unless of course it really is limited by a legitimate 199A restriction).  Fortunately this is not an issue for K-1s you import from PTO that your firm prepared as they come stripped of commas.  But if you enter a K-1 you didn't prepare, and your not really clear on the rules, you might not catch that a deductible 199A deduction is being blocked by a software problem.

PTO allows you to enter commas in numbers everywhere else I'm aware of, I don't know why this section has this problem.

Note:  I use Google Chrome (77.0.3865.90)