I agree, it should not pull out via anti-skate, and as you say, you used it for years successfully.
Is the top of the lifting arm’s rubber surface worn/polished too smooth? Fine sandpaper to restore some grip? Even cut some small indentations.
Is the TT perfectly level? check platter separately/check arm post separately. i.e. arm perfectly perpendicular to the platter.
Zero anti-skate: does the arm float or pull in/out when balanced parallel to LP?
You could shim the lifter slightly so that there is a slight rise in the top bar to lift and resist inward motion.