Unusual differences between mastermixes (Sensimix/ABI)

[fluori]

Hi!

I'm completely new to this forum. I joined because I have some unusual dissociation curves with the sensimix SYBR. The dissociation curves from the same samples with Power SYBR are totally different.

All samples (positive, negative and NTC) give the same dissociation curves with the Sensimix SYBR, which is theoretically not possible, since the primers are specific for the positive sample and NTC/negative need to give at least different dissociation curves.
The same samples with Power SYBR mix (ABI, which is developed for our ABI Fast 7500) result in two different groups of dissociation curves: the positive samples and the negative samples/NTC, which is theoretically possible.
(see attachment)

I am wondering how it is possible that the dissociation curves of the sensimix are not specific.

Someone some suggestions??