RESOLVED BY UPDATE - THANK YOU!
No problems firing cannon or missiles, but when I modify a damage beam group I am only able to fire it once. It appears to recharge, but refuses to fire. Tested on multiple small ships and a larger ship with a stable L17, 900-block reactor attempting to fire a 10-block beam. Tested against shielded and non-shielded targets to watch for impact (eliminate possible UI or graphical bug).
If I modify the group, it will fire again. Once.