I ran into the same freezing problem with an older big project using avi files with DivX/H263 encoding that worked fine in Studio 18. When exported in the Studio 20 version, the video was rendered fully, but the file truncated when using Intel hardware acceleration, and freezes randomly with acceleration disabled.

As mp4 files with H264 encoding seems to work fine, but could not be changed in the mentioned project, I have tried anything to get the H263 coded files to work in Studio 20 without success.

Have noticed, that DivX files have become a problem in Studio 20, where some versions does not show the video content, which worked fine in Studio 18.

Have Studio 20 (64-bit) installed on the main computer, and the 32-bit version in a Virtualbox guest, where the export worked fine without problems in the guest version.

Decided to install the 32-bit version on the main computer, and the export now finish without problems, as long as hardware acceleration is disabled.

Conclusion must be, that there is a problem with H263 decoding in the 64-bit version. Cannot recall if I was using the 32-bit or 64-bit version of Studio 18, and installing the 32-bit version of Studio 20 is very tricky.