With only this gif to go by it is very difficult to asses what the issue is. Not knowing if you have those elements in the YR set into their own groups, as well as how you have them set in terms of fixed width.
From what I see in the gif, this is my assessment.
Your setup in the group with the red border has a set of groups that you have created to be used as the table. These may be contained within a repeating group of a single column structure so that you can add what looks like up to 11 groups to represent your year columns…or perhaps it is not a repeating group but just a regular group with 11 groups contained within.
Either way, your groups you are using as the columns for 11 years have hiding rules set on them so they are hidden and their widths are collapsed from inside of their container.
The main problem, is that these 11 groups used as columns are set to fixed width and are not set up properly to have them expand their widths when the extra space becomes available.
To imagine this with numbers. You have 11 groups all of which are 100px in width and contained inside of a group that is 1100px in width. You hide one group when the container goes beyond 1100px, so now you have 10 groups each with 100px so a total of 1000px, but the container is 1050px…that extra 50px your container has is that white space.
If you make it so that those 11 groups you use as columns are not set to fixed width you will fix the issue…put the min width to 99 and let the max width be unset so that the 11 column groups will expand to fill the entire container after each one is hidden with the hiding rules you have set on them.