I suggest you make a new payroll deduction to use as your PMFL deduction and create your own spreadsheet to calculate l the correct amount that should be pulled out- this is my work around. Which means you will then have to hand enter the amount for each employee and each payroll. Takes a little bit more work at payroll, but will save you having to make up the difference. 

Thanks for the suggestion, that is exactly the same way I decided to handle this!  I'll create a withholding category called PMFL Balance and track it by hand until QB finally addresses this problem as they should have done months ago.  Now that my Q3 filing has been made...incorrectly again...I'm not wasting hours of my time dealing with QB help on this, especially when so many WA payroll accountants have already reported that it was pointless and they didn't/couldn't fix the issue.  Unfortunately it means the quarterly report that's electronically submitted by QBO will be incorrect relating to Premium totals per employee (though total gross wages are correct), but I'm notifying WA ESD of the issue (I have a feeling they already know) and will pay the balance due manually until this is corrected.  BTW, my premium withholding % is still stuck at 0.4% where I set it in 2019!