I just contacted UJAM Support about the no-sound issues in all Virtual Drummer REs and got this response:
Thanks for reaching out! Please note that we didn't create a Rack Extension for Virtual Drummer and that Rack Extensions are a different format. Reason is a completely independent shop and will unfortunately no longer update RE. At ujam.com we sell the VST / AU / AAX version, which includes the new features of version 2.
Maybe you first want to try them out? We have 30 free and full version trials of all products
So this is contrary to this response from Reason Studios, as quoted by:
steveg1bbs wrote: ↑29 Apr 2020
Reason support has pointed me at the makers, UJAM, as they didn't code it themselves.
A lot of finger-pointing here, with Reason Studios and UJAM claiming the other party coded the RE. And note that the RE will never be updated in the Shop according to UJAM.
I just downloaded the 30-day free trials of the UJAM VST Virtual Drummers and tried to replace my RE version, but the included Styles MIDI patterns do not correspond to the Rack Extension versions, so it's not like you can just replace an existing Virtual Drummer RE with the VST and get the same result. UJAM VST uses a different naming convention, and more importantly, it does not contain nearly as many Styles as the Rack Extension. It's so different that I feel I will probably continue to struggle with the RE versions and hope it plays properly on export.
UPDATE: I did contact Reason Studios Support and provided the response from UJAM, asking RS for any bug assistance. In the meantime, I ran my VD in a loop and noted that it stops sounding around 10 minutes, which means your song can't be longer than that. A workaround is to record the VD track to an audio track, then mute the VD track, and keep it for future editing if needed.