If you enter an amount for the per min rate on the DID page and use “PSTN” forwarding for the DID, the rate is not calculated. (CDR’s just show 0.00 for the inbound leg)
They take a long while to respond to potential bugs on JIRA.
Probably better to wait for them to respond then they may tell you to post a bug report on there. Then it will be responded to faster, usually.