Things I would check is first off the patches. Find some of the spent patches. Examine them for tears, burn marks, etc. Although normally with a wad, patches do not burn. Also, do you pre lube and then leave the patch lubed? Sometimes pre lubed patchs will go bad. Its a combination of the lube and the patch threads. Try some new patches that have not been lubed.
Also if the temperature is very different from when you normally shoot, this could be a factor. If it is hotter, try cutting the load down to about 105 grains of powder. Sometimes too much powder on a hot day can create a lot of gas behind the ball. Reduce the charge and lower the gas volume.
Also when is the last time you really cleaned that barrel? I had a Renegade .54 that did the same thing. While I thought the barrel was clean, I boiled it out, then brushed it, and then alcohol patched it. The accuracy then returned.
Just some of my thoughts.