Direto II: lost resistance regulation during training

[zdenek]

I have a trainer Direto II. With this trainer I use a cadence sensor and HR sensor. 3 HR sensors from Elite were returned because they survived max. 2-3 trainings and then they were dead. Now I use HR sensor Cateye, which is uncomparably more durable. All system components communicate with my notebook (ASUS, Windows 10) via ANT+ USB dongle. I use exclusively the app Zwift.
Although the HR sensor from Cateye is better than Elite, after some time of the intensive training the Zwift starts to show stupid HR values (e.g. 280 bpm and more), or stops changing the value, or connection with the HR sensor is lost. I guess the general problem is huge amount of my sweat. Very often the real help is usage of my towel to dry out my chest around the HR sensor. But sometimes this incident breaks communication between notebook and the smart trainer.
For example yesterday I climbed up to the hill in Insbruck. Up to 70% of the hill everything was OK and the trainer changed resistance according to the percentage in top right corner of the Zwift screen. Then the HR sensor started to show incredible high HR and the trainer set almost no resistance. I removed the HR sensor quickly expecting some problem. The trainer set the resistance back to value, which matched somehow the current elevation around 8-10%. But then the resistance was never changed. Although I reached the top of the hill and started to go downhill the resistance remained on the value for 8-10% elevation. The only way was stop my training, unplug the trainer and start everything from scratch.
Does anybody of you know what could be wrong? How to solve the problem?