Everything works well until the finish of recording. The master is trying to import slave's recordings but fails. The following message poos up:
Could not download record(s) from some of the slave PCs. Please copy records manually and run 'Merge videos' tool.

Computers are connected with iPhone hotspot.

So, does "manual" merging work for you?

In order to examine the problem further, please provide us trace logs both from master and slave PCs after the error occurs again. To get a trace log, press corresponding icon in the top-right corner.