Bulb temporary unavailable

I have two Feit A19 bulbs from Costco flashed with tasomta and connect with wifi and local mqtt server (which connect to HA). They are used in the outside of the garage door.

From time to time I found that the status of the bulb will temporary report unavailable and then flip back in a seconds. In a few cases this just happens when automation run so resulted in automation failure. Below are some logs I obtained in node-red:

2020-10-20 17:40:07 sensor.feit8_status unavailable
2020-10-20 17:40:07 light.feit8 unavailable
2020-10-20 17:40:08 sensor.feit8_status 32
2020-10-20 17:40:08 light.feit8 off

What could be the reason? Is this due to weak wifi at the outdoor?