Suggest removing the valve (plug the vacuum line from the engine) and baking it in a warm oven or over a heat vent for a few days. If that doesn't help you'll probably have to replace it or do without. Personally I like having the rear headrests down out of the way (if no rear passengers) for better visibility.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970