Strange behavior of rear drum brake

[MikeWard]

Hello, and welcome aboard to the strange train.

I have a long time issue which bother me a long time now.
The problem area is the drum of the rear wheel, and prob. the drum brakes itself.
It all started 2 -3 years ago, maybe after a service i had, where i felt a strange brake behavior. Imagine going down the road with a city speed, and when in need of braking, press the rear brake lever, the front wheel stops good and linear, while the back is intermediate, like too much its like i press and let go the lever.
I thought that maybe its just bad pads, and didn't do anything. On the next service, i mentioned it to the mechanic, and he said he found a weird color and smell thing on the drum brake, he cleaned it and drove off, at first, the cleaning was a solution and didn't felt this thing again.
Not after some km's it just re-apeared. Next service up, i gave a lot of details and tried to make the mechanic see thoroughly this thing, and so he did. The problem was a rubber that hold back the driver gear oil from getting to the drum, was a bit loose, where gear oil was leaking to the brake. i doubt this is a thing because as wheel rotates it would evenly distribute the oil across the drum brake. so i thing that a mechanic used bad brake pads and the wear of the wheel drum is un-even so it brake intermediate.
Have this happened to anyone across Community? i am really confused. About to change the rubber ring and test it after, but i doubt it would change the braking performance.

[gn2]

If you get a pulsing in the lever of a drum rear brake, the most likely cause is the drum is no longer fully circular.
Any lubricant ingress is most likely from enthusiastic greasing of the drive splines when replacing the wheel.

[power-full]

good . will it not have to do with the quality of the wedges? I only use Polini or EBC (I now have the EBC h352 mounted on the back) .. ,in front I only use sintered EBC (ref sfa603hh), on the wedges I usually make some cuts) with a saw blade, which helps a lot to do not allow to accumulate dust and do not let the rear wedges glaze.