shower diverter valve is now hard to activate

. . . after I replaced the showerhead with a showerholder with a metal hose and a handshower. I have one of those Delta tub faucets with a diverter actuator handle at the end of the tap: pull it up for the shower - down for the tub. With water at full pressure, it is now much harder (but still possible) to pull the handle up for the shower. I also need to apply more pressure to force it back into the tub position. With water at half the pressure - no problem. I suspect because of my shower installation, it is harder to force the water to shift from the tub to the shower position, but I do not understand why.
I removed small o-ring mesh filter, check valve, and flow restricter from the shower unit. I think it got a bit better but not by much. I still need to see what happens if I disconnect the metal hose form the showerholder base - it is a bit tricky and I am not up to this challenge at the moment.
I would appreciate an advice.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.