Problem with GGCAT when using 32 threads

[khodor14]

I was running ggcat on 72 human genomes (subset of human genomes used in ggcat paper and published on zenodo). I was executing it with 32 threads. After 24 hours it was still executing so I stopped it. Then I changed the number of threads to 20, it finished in 13 minutes. I tried to monitor both execution settings, in the first case (32 threads) phase eta was always 18446744073709551615 s, while for the 16 threads case it was 1290 s. I am not sure if this is the source of the problem?

Anyway, what could be the cause of such a problem? (it is supposed to be faster when using more threads).

Thank you in advance.