Yep, weird things can and do happen. Rarely do any of them result in dangerous pressures, mainly just inconsistent ignition. At reduced loads a pressure spike is rarely up to the rated pressure of the cartridge. Several folks have documented this stuff 'scientifically' with pressure trace equipment.

Some that can be an issue involve using fillers and/or wads in the case. Incorrectly used they can create something like a barrel obstruction.

But...any who are not comfortable working 'outside the zone' of published data, then don't.