Takes very long to calculate coupon on FE

My customers say it takes a very long time to calculate a coupon discount. I timed up to 45 seconds.
Worst part is that the user is not aware that somethin is being calculated. No 'donuts' are seen, and the checkoutpage looks like it is just sitting there.

Is use

• J!: 3.8.10
  
• AWO 3.5.6
• VM: 3.2.14

What can I do to speed up the couponcalculation?

The calculation should be quite fast.  Sounds like there might be an infinite loop somewhere.  Is it possible to have a direct look at it?  If so please send a private message with temp admin and ftp access.

I have sent you a PM with access details, did you find them?

Thanks, just replied.