Getting only 7 bytes out of full 256 bytes packet

[vtxray]

Using XIAO esp32c3 on Arduino IDE with such RS485 board: https://www.aliexpress.com/item/1005002287645672.html
The board does not have EN pin (I set int enablePin = DMX_PIN_NO_CHANGE). But so far want to receive the DMX messages.
My DMX network sends four packets of data on each command: each time 7, 7, 256 and 256 bytes. Screenshots of the whole command and of the beginning of 256-byte packet is below.
Data in packets (decoded using oscillograph):

1. 0x80 0x01 0x13 0x07 0x42 0x00 0x05
2. 0x81 0x01 0x13 0x07 0x0b 0x80 0x05
3. 0x80 0xff 0xaa 0x01 0x00 (251 times) 0x05
4. 0x80 0xff 0xbb 0x00 (252 times) 0x05

Then I call dmx_receive() and dmx_read(, , packet.size) in the loop (compiled almost without modification Arduino_DMXRead example, just removed disconnect and driver delete part and added some debug output). And getting first two 7-byte packets just fine, but next packets received as 7 bytes packets only.
Debug output:
06:51:10.761 -> Err=0, sc=80, size=7. Received=7. Data=80 01 13 07 42 00 05
06:51:10.810 -> Err=0, sc=81, size=7. Received=7. Data=81 01 13 07 0b 80 05
06:51:10.847 -> Err=0, sc=80, size=7. Received=7. Data=80 ff aa 01 00 00 00
06:51:10.892 -> Err=0, sc=80, size=7. Received=7. Data=80 ff bb 00 00 00 00

Why the lib truncates the packets? Should I somehow reset driver after each packet?
Appreciate any ideas.

Thank you!

[vtxray]

p.s. Kind of found temp workaround - using dmx_receive_num() with exact number of expected bytes.
However I must be able to receive packets of unknown size. How do I do that?