What's causing this Overlap?

we need more information. post example file if possible.

You say switching sheets clears it so what happens just prior to overlapped view? Or does it just suddenly appear.

Can't see the overlap in that image. Are you saying it appears after calculation?

Workbook example would make this so much easier than working with static images.

I can't find exactly what is causing the problem but if I clear the formats then reapply borders and number format to J:L cells the overwriting goes away.

You may want to reconsider the custom number format approach. when not use 2 data columns for ID and description. The user can select via description and you can use a vlookup or MATCH/INDEX formula to get the ID number.