That is very sad. Have you any logs from these flights?
I am asking because headspeed change and GeoLink (any function) has no relation to each other.
Even with a defective GeoLink the headspeed should never change on its own.
So I am afraid there are more things to check.
Our address is at this page:
https://spirit-system.com/contact.phpPlease send the unit to us (if you think it is faulty in any way) and we will check it with our models.
Also please attach a note with your email address.
It is important to declare package value to 10 USD or less. And if possible, please mark it as a FREE SAMPLE or Reason for export: WARRANTY REPAIR. Then the package should arrive safely