Portfolio image display problem (bootstrap)

Hi

I’m looking to find help on a problem with my website. It was built in Bootstrap (using a template which I have customised).

The problem is in the portfolio page (https://bit.ly/3902YMN). When you first load the page the images below the fold are all crushed together and some are small and they overlap and it looks a mess! If you filter them it sorts the problem out, but I’d like it to be correct on first load?

Does anyone have any idea how to fix this?

Many thanks
Mark