Alerts - not all sensors are shown

Alerts - not all sensors are shown

Hi everyone,

I'm hoping someone can help. I've tried the support route and Tago suggested the Community would be a better place for my issue "due to the complexity of the answers"?!

When I select to create an Alert by Sensor the incorrect list of sensors is shown.

If I login as User1 which has 8 sensors - only 6 sensors are available on this list, 2 are missing. 

If I login as User2 which has 1 sensor - 4 sensors are shown in the sensor list, none of which are assigned to this organization.

Tago suggested I delete and re-register the sensor. 

Question: will removing the sensor delete historical data? These are live customer sensors and I can't lose the data. I asked Tago this question but received no response.

I don't want to offer my customers Group alerts so I removed the group section from the Alert form and now no alerts save. I suspect there are bigger issues with this but sadly I can't find any help.
Has anyone else had issues with the Alert form in Tago Run?

Thanks in advance for any help,