Just before my home center started putting out the national's shot on 4 lanes, during practice on Sunday's I was bowling pretty good. I was averaging 220+.  Then I go practice on the national's shot and was doing pretty good. I averaged a little over 200.
Well this past Sunday I decide to bowl on regular house conditions.(I already bowled at nationals so why continue to bowl on this pattern? Won't see it again until next year). I figured since I was having to be more accurate and concentrate more on the tougher pattern, that I would be able to shoot lights out on the THS pattern.  Well to my surprise I only averaged 190 for 12 games. I can't figure out what the heck happened.  I played up 10 out to about 6. First game was 220+, then I was lost. If I got it past 6 at the break, I would hit really light but not carry.  If I tugged a little and went up 7-8 at the break it would go thru the nose.  I also noticed it was way more speed sensitive.  If I slowed it down a little, the ball bit early and went thru the nose or brooklyn. If I sped it up a little, I would slide thru the break and washout or just barely hit the head pin.
I played deeper, 15 out to 10-12. I couldn't carry, ten pin after ten pin. No adjustment seemed to work.  I changed balls but had similar reactions.

It's very few that I have heard this happens to.  They bowl in a sport condition during the summer and average high 190's or low 200.  They return to THS for winter and are still averaging about the same as the sport condition.  Yet before having bowled on sport conditions they averaged 210-220+ on THS conditions. What happens? I just don't understand.
Does anyone have any idea?

My take on it is this:

1) Did you make any surface adjustments on your equipment for the sport condition? If so, they may not react well to the THS shot. Probably not the case, but it is an easy one to fix if it is.

2) Did you clean your equipment properly? The sport conditions have more oil volume, usually, then your THS. If you don't clean your equipment the oil could soak in thus reducing your reaction by the time you get back to the THS shot. This sounds like it might be a possible cause for you. You may need to give your equipment a hot water bath or if your local pro shop has one of the ball oven productsuse that to remove the soaked in oil.

3) Lastly, and the hardest to fix, is maybe you made a slight change to your physical game to compensate for the sport pattern. That allowed you to score well on the sport pattern, but is hindering you on the THS. If you have a video of yourself from before you bowled the sport pattern, compare it to a video of yourself now and see if you can notice anything. This may require getting a coach to evaluate your game and see if they notice anything.

Hope this helps.
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Jorge300