I just received my CarloopGPS last week, so now I can look into how the LIS3DH behaves.
Also, I do not have an AssetTracker, so I will have to ask you some questions.
Accelerometers in general have adjustable sensitivity as well as thresholds for wake functionality.
I was reading about one that had adjustable sensitivity of 2G, 4G or 8G. If the accelerometer is difficult to get quiet, then probably the setting is too sensitive. Note that the lower setting (ie. 2G) is the most sensitive. The threshold setting should be set higher than the background x,y,z variation so it does not trigger unless the movement is big enough that you want to detect it. Both of these should be adjustable in the firmware code.
The other aspect is hardware. Older GPS units to go along with Carloop communicated via Serial1 communications. I have to verify if this is still the case for the new CarloopGPS. The Carloop would always have to monitor the serial line to get the x.y.z in order to detect movement. Does the AssetTracker communicate with the LIS3DH the same way? It could be possible that there is additional connection between the sensor and the interrupt line, but you would have to look that up.