When STP is disabled on EXOS it will forward BPDUs that are received as it should. This causes a newly added switch to have their BPDUs forwarded to another switch running STP and could cause the port to be blocked. This can cause any kind of network outage depending on the port that is disabled.
This is not a bug, but merely a behavior of STP and L3 switches. STP best practices should be used to prevent this issue, but EXOS switches can be configured to stop forwarding BPDUs as a workaround.
Command to disable BPDU forwarding:
Configure stpd bpdu-forwarding off