Advice for a Tuning Setback

My friend Peter W. from London, Ealing who is a novice piano tuner asks me:

In the last few months, I have been having a setback in my tunings. I am experiencing a problem which is adding an extra hour onto my one hour and 45 minute tuning time. 

I am assuming I am doing something wrong. I set the temperament first then usually do the bass next, but because of this problem I go first to the tenor and treble, and sometimes do a pitch raise in the high treble section (after the last break). By the time I complete the bass section, my area above the temperament is flat and occasionally my temperament is out. 

My experience is different with each piano, but as always the treble section after the last break is always flat. This is always a problem when the pitch is 5 cents flat or lo-20 cents flat. Any piano which is over 20 cents flat I do a pitch raise and then a fine tune and I still encounter this problem. I always set the pins and pound out the keys to settle the strings. 

Can you tell me what I may be doing wrong?

Read the answer at my website:

https://www.professionalpianotunerlondon.co.uk/post/advice-for-a-tuning-setback