SE LR64 intermittent level reading issue – sometimes correct, then stuck at maximum (Mastic powder tank)

[VuHo]

Hello,
I am using a SE LR64 (24 GHz) radar level transmitter for a mastic powder storage tank (about 70 m³).

The radar sometimes measures correctly for several hours or days, but then suddenly jumps to the maximum reading and stays at full scale — even though the real tank level remains stable or decreases.
After some time, the reading returns to normal, and later the same problem happens again.

I have already tried the following:

Cleaned the antenna and nozzle area several times (no improvement).

Checked the 4–20 mA output and wiring (signal stable).

Verified power supply and grounding (OK).

The environment is dry powder (mastic), which may cause dust and buildup on the antenna.

Attached are:

Trend611.PrintChart.pdf → shows correct readings at first, then the value suddenly goes up and stays at max.

70m3.pdf → tank drawing and installation details.

Questions:

How can I confirm if this is caused by echo loss or configuration parameters?

Is there a recommended Fail-safe or Echo loss timeout setup to prevent this “jump-to-max” behavior?

Would a guided wave radar (GWR) or purge-type antenna be more suitable for this mastic powder application?

Thanks in advance for your help!
Attached: Trend611.PrintChart.pdf, 70m3.pdf