In addition to checking the control pressure cable, you could have vacuum modulator issues too. Weird 2-3 shifting can be the K1 accumulator spring, it is widely documented on this forum and elsewhere.

Lack of downshift can be the Klima relay, but is also more likely to be the kickdown button itself being bad or the solenoid being gummed up or nonfunctional on the transmission.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]