Found oil in the back today, after looking around it seems to be coming out around the cap on the fill side of the oil tank. Since it' under pressure would it be a seal in the cap? or worse? Thanks

Sometimes the caps can crack, usually from being over-torqued when screwed on. (Power-Pole has this issue also; I had to replace a cap cracked by someone other than myself.) I haven't experienced an oil leak like yours, but I would think that a cap just not quite tight enough might develop pressure but let some oil get past the gasket seal, or past a bad gasket seal even if tightened to specification.

The first thing I would do is inspect the gasket. It could be damaged from age or over-tightening. You might try flipping the gasket over to improve the chance of a good seal. If the leak stops, get a new gasket. Inspect the cap housing for cracks.

Thanks