The replacement tips with the manufacturer product ID 4XH0R14769 are compatible with the Lenovo Active Pen 2, not explicitly with the Pen AP400U. There is no confirmed compatibility with these tips for the Pen AP400U in the available information.
No, with me it was the other way round. The old tip caused problems and the pen works perfectly again after I replaced the tip.
Do you still have the old tip? Can't you try it again?