Nightbot timer doesn't work perfectly

I’ve set up three times, timer on 45, 50, and 55 minutes and 2 lines
They work well before five, but after five they become abnormal.
(see figure)
Can you fix it?

Timers will always execute at the top of the hour. If you choose 55, it will execute at :00 and :55. Timers tend to work better with lower numbers for that reason.