Are they original windows and steel window track channels? If the steel track channel has been replaced, it is possible that too much urethane adhesive or the window bonding strips were not trimmed properly, and they are binding on the upper outer door rubber sealing strips that snap to the top of the door skin.
window track channel:
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1970 K/5 Blazer CST 4WD,
TOTM winner December 2024! Medium Bronze poly, 93k ACT. miles, 350, 4 speed, rear positraction, 16.5" x 8.25" HD Kelsey Hayes wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration finally getting close to completion..
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