Yes its a concern. Try spreading the brake pads just a bit..take the pins out, along with the small metal positioning plate and insert an oval (wooden hammer handle?) between the backing plates and turn until they move away from the rotor a bit. If axle turns OK, be happy. If not you have deeper problems. Apply the brakes and it no longer turns until you repeat above? Then you have either a sticking caliper or a blocked rubber brake hose. Loosen bleeder valve...if it turns now after a bit of fluid under pressure spurts out then its the hose. I'd put my money on the caliper.

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Hanno
'79 6.9 Sold (after 27 years)
'83 280SL, 5 spd.
'94 E320 Sdn. 5 spd conversion
'02 E320 Sdn.(on loan to mom!)
'87 300E (5 spd. conversion) Sold
'05 E500 Wagon