I tested the version 2.38 with H265 in fullhd in Italian on three different PCs, it is good and stable. Only one thing I was lucky enough to try on a server with 2 xeon for a total of 20 cores, however, the processor is used at most 35% as ever? if you could use 100% it would take very little time. thanks for the work done
Sometimes the encode settings can play a factor in the CPU utilization. If it's doing a rescale it might get bottlenecked. If you posted an encode log I could make some suggestions on what might be causing it.
With a 20 core CPU, it may be processing the video faster than it can read it from the storage media, so 35% might be all you get.