Column width constantly resets itself to increasingly smaller chunks

I have a flexible layout, complex page with a variety of columns and regions. All was working well with a near perfect layout but I wanted to adjust the size of one of the columns ... since attempting to do so the size of the columns of the affected row has been completely messed up ... it is as if the overall width for that section of the panel page is missing the final column and adjusting sizes appropriately. I had a 3-column section, fixed regions. I wanted to change the final column from the max width (of about 380px) to 360px but every save simply makes the columns in that row adjust smaller.

I tried removing the entire last column and recreate it, only to find the same behaviour on the two remaining columns but with smaller values (it squishes up the first two columns leaving large empty space on the right).

I am next going to try to remove the entire row and build up the structure again from scratch (cross my fingers and hope) but for future reference, or in case this doesn't work, I'd love to see this fixed and/or know what variable I need to tweek to get the math calculations correct.