HMT not reading hitting balls outside at night?

[Gstmike]

So I bought a net return just to hit balls outside when the weather is nice and the sim room is being used as a theater.
Seemed like as the sun gradually went down I was getting more one dot reading/no reads on my HMT until eventually it wasn't reading at all. Even with clubs with new stickers. Ball data still seems fine. It's not totally dark as I have outdoor lights back there and enough light to see and hit balls.
Tried pointing a spot light at the hitting area where I thought it would give the best club head reflection but no luck. Was still only getting the occasional HMT reading but most were still just one dot readings or no club data at all.
Is there a secret to the amount and location of light that needs to be present for the GC2/HMT to consistently pick up ball and club to get all data?
I never noticed this even when playing in the sim room with the lights dimmed to maximize the projected image.
I will verify HMT is still working in the light of day tomorrow but wondering what advice others might have.

Thanks

[Gstmike]

Wow. Still not even one response?
After testing further in the light of day, it seems it may be related to the club stickers I am using. I have my previous version of irons that are only used indoors with the sim. Those have the original clubhead stickers provided by Foresight with my HMT. The clubs that I play real golf with are the ones that I am constantly changing the stickers on. When I ran out of the Foresight stickers a while back I purchased more off of Ebay at a more reasonable price. But it seems that these do not hold up as well. The indoor irons that still have the Foresight stickers seem to consistently show clubhead data but the Ebay stickers that I haven't really had a problem with indoors to this point seem to not last as long or stay reflective when clubs are left outside in the heat? And it seems I am having to change those stickers after only a few hits?
Unfortunately I am just about out of stickers so I ordered more from the Ebay sight before I discovered this so I will also be ordering more from Foresight (that are much more expensive) to compare and see if these OEM stickers do in fact perform better in lower lighting conditions.
I'm still hoping others will chime in.