Dirt is usually the culprit in one form or another. If you don't want to do the complete overhaul for some reason, the specific dirt I would look for here is a gunked up switch where the trigger rides on the way down. Clean up all those switches. Then use the lightest bit of teflon lube - the stuff you use on steppers, on the active switch blade. The other thing you can do is to adjust those switches so that they are not initially in contact, but once the target gets moving they hit the switch and the switch closes for just a brief fraction of a second. This helps the assembly build some momentum. Clay taught me this trick. It works well.

The spring is wrong. To fix it correctly, you need one like you have on the other side.

That said, if the reset bar is dropping out of the way of the trigger arms, this isn't your issue. If the reset bar is not falling completely on it's own, then the spring is likely the culprit.

https://www.marcospecialties.com/pinball-parts/13455

http://www.pbresource.com/bigindian/bidt.jpg

Also, I wrote a guide on a complete overhaul and did a youtube on it as well

http://www.pinwiki.com/wiki/index.php?title=EM_Repair#Drop_Targets

The jpg referenced earlier from Pinball Resource shows this spring in assembly.

A bank that long should probably have two. There is no downside to having two.