Repair issue on ONE+18V Sawzall (not brushless)

So I was able to replace the broken slide rod and attachment clamp without any real issues, but now it has very little power with any resistance. It seems to run at full power, but while cutting, it isn't working with the same umph. Almost useless.

Any suggestions for what might be happening or how to fix?

(yes, I know a sawzalls are not that expensive to replace, but I wanted to keep this thing going.)