I have the upgrade(3.3) for 4.25.3.  About half of the cc3 characters have holes in the clothes.  Only appears when they exported into 4.25.3.  I guess cc3 is a work in process.  Too bad it cost me $145.  Reallusion do ever test your products?  

Works fine here , did you confirm your cloth in CC3 or transfer skin weights?
You also can use the hide body mesh tools in CC3.

Baseline if you have time would you make a video using cc3 3.3 and 4.25.3.  Use the 3 person template.  Do a couple cc3 characters.  And put it on youtube.  All of Reallusion videos are over a year old. Thanks.  This video is good but not up to date
https://www.youtube.com/watch?v=KIQupdGzr-A&t=44s

Here is a character I just made.

When you do the export from CC3 did you check the option to "Delete hidden mesh"?

It should help by deleting the parts of the character which are always covered by clothes, both removing the chance for them to peek out and also improve performance by reducing the number of polygons being exported.

Yes.