Don't recall ever seeing a report of sound vanishing mid-project; it's either there or it isn't.
Confirm whether the problem is with both PCs? The laptop is AMD; is the other Intel?
Does this occur with the unedited file, or only after you make changes, add effects, etc.?
Though this is an audio issue, try the None(CPU only) setting under OPTIONS | ADVANCED |GPU PROCESSOR.
The three files that you linked above each loaded in a minute or two, played flawlessly and exported losslessly in less than thirty-seconds. #10 has left-channel audio only, while the others have better quality two-channel sound.
As the issue cannot be replicated here, suggest that you install the latest release. Consider a REVO uninstall prior to this.
Clear Unused Cache Files before starting each new project.
If the happens with a 'raw' file, please upload and share it. If audio cuts out after editing, share the project, as instructed above.
Let us know.