200A Key Reset Issue

[arcsound]

I have a late 70's 200A that appears all original, including no regulation work.  It plays well and sounds good, but when played lightly, some keys apparently don't reset the jack properly, and the next play of that key is silent.  Doesn't happen when played forte.  Seems more prevalent in bass section. 
Is this likely a lost motion or let off issue, or a tight pivot?  Any tips on how to best diagnose and resolve?  Thanks!   

[pianotuner steveo]

Letoff. Hammers are letting off waaay too early. Tool is available on eBay. This is very common with Wurlitzers.

[cinnanon]

In addition to the letoff, you will likely need to lubricate the action centers and ease the keys while you're in there. If it's never been worked on, setting letoff alone won't fix the problem entirely. Make sure the notes play the same way with/without the sustain pedal depressed.

[pianotuner steveo]

Lubricate those trouble jacks first with Protek. Also, if this is happening on the treble end, be sure the hammers are not catching and hanging up on the Reed bar on their way back down. I just saw this problem 2 days ago.

[DocWurly]

This is usually a lost motion issue-- that is, the lower capstan, between the key and the jack.