Units not deducted from accumlator

[CyberSleuth]

Here's the scoop:

I'm a Microsoft Professional new to the ins-and-outs of the tanning industry. I got a crash course when my sister-in-law opened the new location for her 8-year-old hair & tanning salon. They've got 4 new beds (2 beds, 1 stand-up and a sunless spray-spa) wired to a TMax Manager Pro and are running Helios v11. Regular beds utilize sessions, while the sunless requires units.

I flew out and setup the hardware and got the software configured with sales codes, etc., etc. They’ve been using the system Since April 5th without too much difficulty, but are noticing some oddities with the sunless. Occasionally -- maybe 1 out of 10 visits -- Helios will turn on the sunless spa without deducting a unit from the customer's accumulator. This does not seem to be happening with the other 3 beds (using sessions,) only the spray spa (units.) They haven't noticed anything being done or the system reacting differently from other times when it works, except that:

1) There’s no record of the transaction in the customer’s history and
2) The name of the ‘next-to-last’ customer that used the sunless continues to be displayed in room status.

Any ideas on what could be going wrong?

Thanks,
Todd Stewart