Cannot recall parked calls

We’re having trouble sometimes retrieving parked calls. Reception takes the call, parks it, and then gives the Lot number to the intended recipient. When they dial that, they can’t always pick up the call. Reception then is unable to pick it up as well.

We’ve a single parking lot, using 40 as the Lot extension, 41 as starting position, and using 4 slots. We rarely have more than one call parked.
The timeout is 180 seconds, and are using the “Next” method for Find slot.

All our internal extensions and Ring Groups are 3xx so there shouldn’t be any conflict.

Version is FreePBX, calls are coming in from a DAHDI E1 trunk.

What log information should I be looking for to help diagnose the issue?

what version of the parking module are you using?