Excel formula disappears - random columns / with no reason / not all formulas disappear

Dear Forum Colleagues,
I hope my message finds you well!

Please, I need some support.

I have been working on some workbooks, which are behaving unexpectedly when it comes to formulas.
These workbooks have different tabs and some columns with formulas and other columns with no formulas.

The workbook is randomly replacing some formulas for the actual formula result as text, when I do changes in workbook.

Example:

The [TAB 01 - Column AC] has formulas ( SUMIFS for example), which get information from [TAB 02 - Column Q].
Eventually, when I am including / typing / copy and pasting information in the TAB 02 ( In any columns ), some formulas in the TAB 01 are replaced for the actual result calculated at one point of time, without any warning from the excel.

I even have to manually check which columns had the formulas replaced.

This type of issues never happened to me and it is strange once there is no pattern.

Please consider:

>> There are NO macros in this workbook
>> There are other formulas which are not replaced by the results ( I cannot understand the logic )
>> The file is stored in my laptop ( Not in a sharepoint / different network )
>> There are no links / calculations involving other files ( Only a BW Query, but it never impacted )
>> The formulas used are simple, such as INDEX / COUNTIFS / SUMIFS etc

Finally, I used this / similar files in the past and it used to work fine... I don't know why this error started.

If you have any idea what could be the issue, I would appreciate to have your support.

Thank you very much in advance,

Max Lima

Welcome to the forum.

This is a known issue. When it happens, remove the formulae from the column, set the column formatting to GENERAL and then reapply the formula.

Just changing the column format alone will not work.

Attach a sample workbook and I shall have a look - it's likely that you are not doing things quite correctly, but I need to be able to check.