BLS stuttering/freezing, especially when towing a trailer

Hello everyone,
"For some time now, I've been experiencing a problem with the engine cutting out or stuttering."

The jerking initially occurred occasionally (~1 time every 50 km) and lasted for about one second, during which the engine would cut out at a frequency of approximately 2 Hz. (Similar to a rev limiter on gasoline engines).
Recently, the jerking seems to have changed, and now it's only occurring as brief interruptions of about 1 second, which feel like the engine is temporarily not getting any diesel fuel.
This error typically occurs in the following situations:
- very often occurs during highway driving with 4 people and a 500 kg trailer.
- during gentle acceleration at 1800-2500 RPM in 5th gear.
-during gentle acceleration in the third gear while going uphill, at an engine speed of 2000-2500 RPM.
- during downhill driving and with low load (instantaneous consumption > 1 L/100km).

So far, I haven't experienced any issues with the first and second gears.
There are no error codes stored in the system's memory, although I once had a brief instance of the following P0403 EGR valve fault code stored.

001027 - Exhaust gas recirculation valve (N18).
P0403 - 000 - Malfunction - Intermittent.
Environmental conditions:
Error status: 00100000
Error priority: 1.
Error frequency: 1.
Lost Count: 255
Time: 0.

Environmental conditions:
Speed: 0 RPM.
Speed: 4.0 km/h
Key press ratio: 0.0%
Voltage: 13.30 V
Air mass/Flow rate: 0.0 mg/H
Key press ratio: 17.4%
Binary value: 00110000

Readiness: 0 0 0 0 0



Key facts:
1.9 TDI BLS engine.
DPF approximately 35 grams of particulate matter.
142,000 km
No tuning.
The diesel filter has already been replaced.
The differential pressure sensor was already defective and has been replaced with an original part (Bosch).

VCDS values:
Synchronization angle: -0.3°.
Fuel injection deviation at 819 RPM:
Z1: -0.54 mg/H
Z2: 0.19 mg/H
Z3: 0.24 mg/H
Z4: 0.07 mg/hour.
Switching times at 819 RPM:
Z1: -42
Z2: -48
Z3: -42
Z4: -50
Exhaust gas recirculation:
Set Point: 240 mg/H
Value: 495 mg/H
Control setting: 100.3%, speed: 819 RPM.
Boost pressure control:
Set Point: 1091.4 mbar.
Absolute value: 1040.4 mbar.
Control achieved: 80.7%, at 819 units per minute.

The boost pressure and EGR tests in VCDS show no abnormalities.
What measurement blocks should I record in order to investigate the causes of the interruptions?

Greetings.

Autoscan.