excessive size of contact sheet

I recently made a contact sheet following the same steps I've done for years. It came out to be 9 GIGAbytes. This is a significant difference from what I used to get.

I found a contact sheet I'd made just a month prior. It was only 69 MEGAbytes.

The two projects were similar: the 9GB contact sheet was 289 photos, while the older 69MB sheet was 269 photos. Same cameras too so the original photos should not have had a significant size difference.

Did something change in Lightroom? Is anyone having a similar experience?

FYI: I have found a workaround (still using Lightroom only), but it takes much longer.