Fatek PLC modbus write

I have a strange M flag write problem after migration from OH2.5 to OH3.2.
The example code below works perfectly in OH2, I can set M38 to “1” with sitemap button, logs say “Item ‘M37’ changed from OFF to ON”.
However in OH3, when I push the button the log only says "Item ‘M37’ received command ON
" but the M38 flag stays OFF and no info about value change.
Any ideas why this happens?

My definitions in both OH versions are identical:
Thing data M38 [readStart=“2038”, readValueType=“bit”, writeStart=“2338”, writeValueType=“bit”, writeType=“coil”]

Switch M38 “test” (g_testgroup) {channel=“modbus:data:fatek:M1:M38:switch”, autoupdate=“false”}
Switch item=M38 label=“Mtest” mappings=[ON=“START”, OFF=“STOP”]

OK problem solved :]
I spotted the cause right after submitting the first post - it’s readStart=“2038”, writeStart=“2338”.
It works fine after changing writestart to 2038 but no idea why it works like that in OH2.