I tried to store timestamps as long values, when I noticed the issue. So yes, the values were ‘true’ long values.
The value in my local CBL instance remained a long. The issues was only after the the value is synced once. Then it is stored wrong in the gateway/server and on any other device, which syncs it from the gateway.
The issue seems to be same, I tested this also with gateway and CBL android version 1.0.4
My current workaround is to simply store the long values as Strings and parse them back when reading.