I recently had the same issue with my Bosch B1450 (I believe is extremely similar to the 1613 EVS). The weight of the router itself as well as the spring pressure would allow it to drop slightly during use.
My solution was simple:
- With router fully plunged and locked I took the screw out for the yellow plunge lock lever.
- I removed the lever being careful not to lose the small washer, screw and spring to expose the locking screw.
NOTE--> The locking screw is a left-handed screw; to tighten turn 1/4 turn CCW (vice CW for tightening of standard right-handed screws).
- Then I put about an extra 1/8-1/4 turn on the locking screw.
- Then I reinstalled the lever. I can still use it like normal, but now I have a little extra travel to really tighten it down when installed in the router table. It is still possible to slip under heavy use, especially with hardwoods, but with easy feed and sharp tooling I have not noticed any issues.
- If you try this and it still slips try tightening a little more. That is if everything else mentioned above checks out and is in good working order. (fine adjustment not loose/slipping and router is not loaded up with saw dust.) If the router's home will be installed to the table then pulling the springs out is not a bad idea.
Hope this helps.
PS: Router table being used is Bosch RA1171 Benchtop Table. Using the 1613 mounting holes.