[wscr]

On newer versions, DHCP doesn't work anymore through a Client Bridge. With r38159 it still worked perfectly. Is there a bug or do I have to change any settings ?

[kernel-panic69]

On what build and router?

https://forum.dd-wrt.com/phpBB2/viewtopic.php?p=1174497#1174497

I followed the wiki to the letter pretty much on that one and it works fine.

https://wiki.dd-wrt.com/wiki/index.php/Client_Bridged

[wscr]

primary: TL-Archer-V2 r40559 (it works with r38159)
CB: TL-WDR4300-V1 r40559

I verified the settings on the CB according to the manual:
https://wiki.dd-wrt.com/wiki/index.php

DHCP works perfect with r38159 on the primary, but not with newer builds (build on CB doesn't matter).
When I go back to r38159 just on the primary, it works again.

Something must have been changed in newer builds, but I don't have a clue...

[kernel-panic69]

Somewhere in the 39xxx changeset range, udhcpd was removed, so if you do not have dnsmasq configured on your primary router, then that could be the problem. That's my only guess. You must configure dnsmasq as your dhcp server after those changes.