Phantom currents with Smartshunt

I have noticed that at times the Victron SmartShunt IP65 500 A I have installed in my camping trailer incorrectly reports currents drawing on the trailer battery. These phantom currents usually range from 2 to 20 amps, last for an hour or so, and appear about every other day. I can find nothing that is actually drawing these currents, and the battery does not appear to actually be discharged as measured by its voltage and the time it takes to recharge it to full charge.
The SmartShunt installed on my camping trailer to monitor its 100 Ah lithium battery. The SmartShunt is installed in the prescribed way with a short cable attaching the shunt’s “Battery Minus” terminal directly to the to the battery negative post. The shunt’s “Load Negative” terminal is connected to the trailer chassis ground to and to a short pigtail to which I sometimes attach a solar or NOCO charger.
In the most extreme example the reported discharge current draw fluctuated between 20 and 500 amps (briefly 900 amps!) over a period of about two hours. The Victron Connect app reported that 550 ah had been consumed! (As noted, this is a 100 Ah battery). After this period the amps reported settled back into the expected range of -0.1 to -0.3. I examined the trailer and there was nothing unusual and the battery remained functioning as normal with a voltage in the range of 13.6 V. At the time this happened the trailer was parked beside our house, no shore power connected, and the battery disconnect switch engaged (ie- the battery was not connected to the trailer electrical system). On this trailer the disconnect switch disconnects the positive cable from the battery from the trailer system. I have not found anything on the trailer that remains powered once I engage the battery disconnect and have not found anything connected to the positive lead between the battery and the disconnect switch.
This episode occurred the day after I had performed a zero calibration on the Smartshunt. I had hoped this would fix the problem of the phantom currents, so I disconnected the wires from the Load Minus terminal and activated the zero calibration in the Victron Connect App. The App reported zero current after calibration, so I had hoped things were fixed. The next day I checked the battery with the Connect app and found the situation as I described above. I will attempt to post a screen shot for my iPhone showing the reported fluctuating current.

This battery is on the back bumper of the trailer so I had to install the Smartshunt in the battery storage box with the battery. The shunt sits directly on top of the battery. Could this cause these problems? I also noted that the reported current fluctuated highly as I tightened the bolt to reconnect the Load Negative terminal. Could over tightening or under tightening these bolts cause these problems?