Your HDD may be too slow to react properly to your Lightroom commands.
Alternatively, the E15 PSREF says:
Get a ~250GB M.2 2242/2280 SSD and install W10 on there.Up to two drives, 1x 2.5" HDD + 1x M.2 2280 SSD or 1x 2.5" HDD + 1x M.2 2242 SSD
Then put a 2.5" SSD in the main drivebay and use that for your Lightroom experiments.
Or maybe dump Lightroom for something else?