Don't know...not enough info for me.
But I have heard this situation many times and for years.
From my experience, everyone wants to blame one thing.
Most of the time, it is not just one thing. Combo of more.
Number one top level cause is usually form. Not saying this is your cause but it is the king.
Also buying a racquet ( with it specs) that is not a fit for you, can also cause players to be late and more..
String setup (no clue what are using), lot of these issues are amplified by players using copolys strings and they can no benefit from them. Plus they add to strain and impact.
High tensions...coploys...over 52 lbs..also stiff strings ...if so, better have good form.
Not going though a good deming cycle. Finding the right frame for your game, do it right and it picks you. Not too light - not too heavy....just right....like that little chick and the bears..
Also PD vibration is:
http://twu.tennis-warehouse.com/cgi-bin/vibfrequency.cgi
Overplaying, no stretching, no post recovery, hydration, resting, mending...compression gear for post recovery also,
All recs (i dont care what level) will anyways benefit from another eye & coach (lessons - some one good).
Thats all I got now.
Hope that is a help or a guide..
Glad you are back in the game.
Be logical, be open, stay away from the hype, listen to your body..it is pretty smart, so are you...
Note: been playing and in the industry for a very long time. I been volunteering for my local USTA for years..focusing on help people get into the game. gliding them with obtaining the right equipment so they can play long and safe...and more...
best of luck