I have Venus is running RPI. Mopeka pro200 tank level sender. Tank is set to 140L. Randomly, it resets back to 200l equaling 7%. But the tank is currently empty. .
I am not sure about the volume resetting randomly, not happened in 3 years using 2 Mopeka senders on a Cerbo GX.
On the offset on older firmware when empty I found that in the Venus settings I had to set the empty level at 7 to 10% of the full level to avoid the zero offset. I assume that there was a bug in the Victron implementation. This appears to have been solved at some point because my tanks are now reading correctly at empty with the latest firmware.
Put a screenshot of the current settings and se sensor reading from the GX setup for the tank.
See how sensor value is 20cm and capacity is 200L.
If I set it back to 140L and match the 18.9 cm is reads empty. ( which it is ) I’ve had to change it back every few days.
You have told the GX that empty is 20cm but the current sensor reading is 18.9cm ie it is 5.5% full (or 6 rounded up).
The GX is just doing what it is configured to do.
If the tank is currently empty and the reading is 18.9 then the empty value needs to be set to 18.9.
The % will be calculated as ratio of the full and empty readings you set. The capacity will be used to determine the remaining litres, only that value should change if you adjust the capacity.
That’s the issue.
I HAVE set the correct value of 18.9 cm and 140L capacity. Multiple times now.
It REVERTS BACK BY ITSELF
Gotcha.
That is weird.
Ok.
Can you confirm the GX version?
Is this a new sensor you are using, if not, did it work before?
Does it do the same on UI version 1?
This may be something Pi specific.
Perhaps the device is being lost and rediscovered as new rather than settings changing?
Certainly my mopeka’s are working as expected.
Is this a top mounted or bottom mounted sensor. I am used to botyom mpunted so level when full should be higher than level when empty. Again not sure about the resets.
Top mounted
Hey, I have this exact same problem. I was just out here searching to see if someone had figured it out and saw this on-going thread. I just connected my Mopeka bottom mount sensors (3 of them across 3 tanks) and every time I set them up and everything looks great in the Cerbo, within a day it resets everything back to the way it was when it first connected, which is completely in-accurate. This happens to all 3 sensors on all 3 tanks.
Attaching an example of what it reset itself too every time. If I set Capacity to 9gal, 0.0cm empty, 52.0cm full, save everything. It stays that way for like a day, and is accurate, some tanks have less and it correctly shows the % left based on the correct sensor values, after a day or so it resets to the screenshot example.
CerboGX is on the latest firmware of v3.60, and all Mopeka sensors are on latest firmware and are the latest hardware.
Anyway just wanted to share myself having the same experience as @kennykustom if anyone has any ideas.
Hi all,
See here Mopeka Universal Sensor Setting Not Holding In Cerbo - #9 by mpvader.
Found and solved.
Thank you for all the reports 
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Fantastic! Thank you for the quick fix. Will test ASAP.
Updated and reset the values.
Will monitor
Thanks for the update !
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Working well.
Heading over to report a different bug
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Can confirm this has worked perfectly for 2 weeks now on the beta release. Thanks again!