Second drive temperature gone after each restart

I have apparently two separate sensors for the two harddisks in my laptop. They show up as separate entities in the output of sensors:

drivetemp-scsi-0-0
Adapter: SCSI adapter
temp1:        +31.0°C  (low  =  +0.0°C, high = +60.0°C)
                       (crit low = -40.0°C, crit = +65.0°C)
                       (lowest = +28.0°C, highest = +31.0°C)

acpitz-acpi-0
Adapter: ACPI interface
temp1:        +58.0°C  (crit = +200.0°C)

thinkpad-isa-0000
Adapter: ISA adapter
fan1:        2229 RPM
fan2:        65535 RPM
CPU:          +58.0°C  
[...]
temp8:         +0.0°C  

drivetemp-scsi-4-0
Adapter: SCSI adapter
temp1:        +49.0°C  

Whenever I restart the XFCE panel, one of the sensors is gone again. I always have to manually set it up again, with name and temperature range that I want it to have. But in the configuration file .config/xfce4/panel/xfce4-sensors-plugin-19.rc I do see the correct entry:

[Chip1]
Name=drivetemp-0
Number=1

[Chip1_Feature0]
Address=0
Name=d2
Color=#00B000
Show=true
Min=2
Max=60

[...]

[Chip4]
Name=drivetemp-0
Number=4

[Chip4_Feature0]
Address=0
Name=d1
Color=#00B000
Show=true
Min=20
Max=60

It's not really predictable, if d1 or d2 is gone after I restart the panel but I have to set up one of them again each time, and it's always the one that shows up second in sensors (the one called with 49°C above).

This is with the xfce4-sensors-plugin 1.4.3-1 package on Debian unstable.