This article explains the behavior of traffic interruption during VRRP failovers.

During a failover event, we may observe traffic interruption for few seconds and seen RTO "Request timed out" in the network.

VRRP election occurs based on advertisement timers and thresholds. With default advertisement and threshold values, the backup router detects loss of primary within a few seconds and assumes the primary role, which may result in brief traffic interruption during that transition which is expected.

Reason for short traffic interruption:

1) During failover, once backup detects Master is down, backup waits for VRRP advertisement timeout (default is 3 seconds).

2) When backup transitions to Master role, virtual IP/MAC ownership changes.

3) Due to traffic reconvergence, ARP cache and MAC table gets updates and refreshed.

This behavior is inherent to VRRP protocol and is considered normal.  

For more information, please refer: https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/statement/failover-delay-qfx-series.html

https://www.juniper.net/documentation/us/en/software/junos/high-availability/topics/topic-map/vrrp-understanding.html#id-vrrp-failover-delay