Welcome to the forum!

Sorry for your problems, DTC code of 147 can be a one way bearing going out(sprag bearing) inside the transmission, and on 1st generation 722.6's this bearing is known to be a problem, but you could be low on fluid, and one of the regulation solenoids could be bad. I kinda think it is a solenoid as it will give you the symptom of okay for a week, and then limp mode. You can replace both regulation solenoids from a junk car 722.6(any 722.6 car). The solenoids are about $300 each. The next thing is under the solenoids is a mesh-filter. It could be blocked, so those need to be blown-out clean, or replaced. The valve body will have to come down, and at that point you will be able to inspect the black speed sensor for cracks on top, or blister breakage.

I Have uploaded a document called 722.6_ETC_Error_code, and it is all about the 722.6 trouble shooting. See post 22 on this thread, and look at pages 52 and 71.

No Transmission Fluid Symptoms - Mercedes-Benz Forum

By the way, you need to have a testing dip stick check the level. You can by a dipstick from peach parts. If the fluid is ugly, change the filter and fluid. Do not do the measure out fluid method, and pour the same amount...

All the best to you,

MArtin