First you will need to work out if you have a problem with the deck or the deck lift .
So pull the deck right off , park the mower on a flat level surface drop the deck lift to the lowest position and using a square measure he height from the ground to the top of the deck retaining pin hole .
They should be the same .
If not then your lifting arms need careful attention
View attachment 54578
Places where problems occur
# 23 (both sides ) missing , worn or backwards, also check the hole they sit in for wear.
# 3 As above, note the pin they sit on is not shown in drawing
# 25 wear
# 26 worn or omitted
# 18 fracture or bad wear or frame rail damage under it
The easiest thing to do is to pack under # 18
The position of the lift handle is badly placed in this diagram so the free end looks like it is part of the shaft axel ( unlisenced CAD driver )
Next is the deck itself
Flip it over and check that the blades for a continious strait line left right
I use a steel rule to extend the blades to the deck sides then trace the rotation of the blade onto the deck with a sharpie pen.
DO each side of the blades and the deck
You should end up with a single strait line right around the deck
A double line = bent blade
Sloped line = bent deck at spindle housing or bent spindle ( very rare )
Also check the welds where the lift brackets attach to the deck for cracking or the deck being bent near the welds ( from people standing on the deck or the mower being slung by the deck )