Boston vertical tuning stability?

[John Minor]

I recently tuned a Boston vertical model 111 and had a difficult challenge
in keeping the tuning where I put it. The piano was close to pitch with
the low tenor being slightly sharp. This section kept creeping sharp even
after multiple passes. The final pass found most notes in the temperament
section to be 2 cents sharp. This is my 3rd tuning on this piano in 2
years and it is only 2 years old.

The home is kept at 57 degrees F during the day and 62 while occupied.
Could this have a negative effect on the tuning stability.

Anyone else struggle with this Boston model?

John Minor
University of Illinois