I should have seen this one earlier. When I got my Burb, the door actuators weren't reliable or functional at all. I replaced one and had the same, disappointing, results.
So, I went after the inside door handles, actuator rods and their plastic guides with much greater success.
Removed the rods from the guides but, not from the door, and cleaned them of all the gack that accumulated along with some rust with WD-40 and steel wool.
The plastic guides I hit with WD-40 and rags. I then lubricated the rods at the guides with White Lithium grease. I did have to replace some of the clips and that ended up with a trip to the Steelership but the damage wasn't what I expected.
Door handles were removed, cleaned and Lithium Grease applied. I need to replace the PS Rear door unit as it just doesn't want to cooperate. Dorman replacements are around $20 at O'Reilly's. Actuators, depending on the door can run up to $70 at LMC. Haven't checked Rock Auto's prices on either the handles or actuators.