Build size (pak/ucas) much bigger in UE 5.3 vs 5.1

We recently upgraded a project from UE 5.1 to UE 5.3.2. Our total pak + ucas size for Windows Shipping builds used to be around 9GB after compression, now it’s around 15GB. We haven’t changed anything major when it comes to build settings, compression or other, but it seems from the file lists in both pak and ucas files that more or less every file is larger, often 3-5 times larger.

Are there any config changes or similar that changed from UE 5.1 to 5.3 that could cause something like this? We have looked over things like Oodle settings, packaging options (for UAT), texture group settings, etc, with no luck so far.

Any help would be greatly appreciated!

A bit of extra info to my question here: It seems like the worst sinners are materials, and especially material instances. Lots of them have tripled or quadrupled in size, which seems very odd. For example, a material instance that was 4MB uncompressed, 3MB compressed, is now 12MB compressed. Not really sure why material instances are that big to begin with?