I ran into the same issue as described above: broadcasted ARP requests were not replied from one client made to another client. However ARP requests form a client to the AP (and vice versa) worked.

Tried every possible hostap configuration option without success. The solution was also to use another wifi adapter (tested mutliple times):

• The adapter that did not work was a TP-Link TL-WN722N v2 (chipset: Realtek RTL8188EU) + installed corresponding driver form the aircrack-ng repo
• The predecessor TP-Link TL-WN722N v1 (chipset: Atheros Communications AR9271) worked as aspected.

I ran into the same issue as described above: broadcasted ARP requests were not replied from one client made to another client.  However, ARP requests from a client to the AP (and vice versa) worked.

Tried every possible hostap configuration option without success.  The solution was to use another Wi-Fi adapter (tested multiple times):

• The adapter that did not work was a TP-Link TL-WN722N v2 (chipset: Realtek RTL8188EU) + installed corresponding driver from the aircrack-ng repo
• The predecessor TP-Link TL-WN722N v1 (chipset: Atheros Communications AR9271) worked as expected.