Wifi clients disappear from arp table

[krzyq]

Eversince upgrading to the 3.0.0.4.374 (merlin 32) I have a problem with waking-up my wifi clients after some time of inactivity. That was working fine on stock 3.0.0.4.276 (I made a switch from stock 274 to merlin 374.32 with resetting all settings).
Now the situation is that when my wifi client goes to sleep, I can wake it up using ether-wake for some time (like a couple of hours or so), but if it sleeps longer, it's no longer possible. I've noticed that this seems to coincide with the arp table changes. After being idle for some time the entry in arp table changes from:

(192.168.0.210) at 7C:xx:xx:xx:xx:xx [ether]  on br0

to:

? (192.168.0.210) at <incomplete>  on br0

Now, the questions part:

1. Could the disappearing arp entry be the case of my inability to use wake-on-line?
2. Can this behaviour be configured?
3. Are you aware of any changes between stock 274 and stock 374 or between stock 374 and merlin's 374.32 that would affect WOL somehow?

Please note that my wifi client are on static DHCP leases. Also there were no changes in wifi settings on client side and clients are configured to allow wake-on-line on wifi card (as it was working before). I will be grateful for any suggestions/ideas. In the meantime I will play with permanent arp entries to see if that changes anything.