Static arp is not set if another entry is present.
Reproduce the problem:
show ip neighbors interface br3003780 Address Interface Link layer address State -------------- ----------- -------------------- --------- 194.55.234.49 br3003780 FAILED
set protocols static arp interface br3003780 address 194.55.234.49 mac 00:15:5d:a6:1a:01 commit
show ip neighbors interface br3003780 Address Interface Link layer address State -------------- ----------- -------------------- --------- 194.55.234.49 br3003780 FAILED