Some cells not calculating

Only SOME cells, from SOME rows, even though the setup is identical to other rows. Info:
- Preference is set to calculate sheets automatically.
- I don't know if it matters, but I am using "set precision as displayed" so auditor hand checks with a calculator will match.
- Limit iterations doesn't seem to matter on or off.
- This has been reworked from a sheet someone unknown made at some unknown time in the past. I rebuilt it as the password was AWOL.

Here's the deal:

I have some sets of cells in a row which multiply together into another column Q:
=(K45*M45*O45)/60
It's taking occurrences per day, times minutes per occurrence, times occurrences per week, converting into minutes, 3 decimal places. This part is always fine.

there are a number of these rows, for different activities. Then they all get added up:
=SUM(Q45:Q48)
or, in another spot with the same kind of problem, the formula is done like this:
=Q53+Q54+Q55
These are displayed to two decimal places, in a cell composed of several merged rows and two merged columns E-F. Merges are because this was made to match an ancient paper form.

The same number is then copied to another column, also to a cell composed of several merged rows, in column I:
=E45

AND NOW FOR THE WEIRD PART:
If I update K or M or O, column Q updates fine-usually. BUT, if I change certain rows, columns E-F and column I do not update! (Unless I click on those cells).
If I change other rows in their range, it all works.

For example, if I update K45, M45, O45, there is no recalc. But change K46/47/48 or M46/47/48 or O46/47/48 and update is fine.


Similarly, row 53 doesn't update, but 54 and 55 are fine.


I've copied/paste special the formulas, I've rebuilt them from scratch within the cells...it's just driving me cuckoo.