MH fails to ignite

Im growing under a Lumatek 400w MH bulb with a MaxiBright DigiPro ballast.
Im currently vegging at 24/0 but i want to change it to 21/3 or 20/4 but my bulb sometimes fails to ignite.
Then i manually have to plug the cord out and in till it powers up as normal.
This keeps my away from using a timer for automating my lightschedule.
Anyone else had issues like this?
Bulb is brand new, ballast i got from a friend but think its a virgin aswell.

Cheers

Put a meter on the cord going to your ballast to see how much voltage drop incurs when the light comes on with the timer. Lumatek MH bulbs won't ignite if there is even a 5% drop in voltage when they are being heated / warmed up. That's why I quit using Lumatek MH bulbs with all NON-Lumatek ballasts. Anyway... from personal experience when I ran some MaxiBright DigiPro ballasts, the Sunmaster, IPower, and the Vivosun MH bulbs work good with the MaxiBright DigiPro ballast, and the ones that don't work so well with the MaxiBright DigiPro ballast include.... Eye Hortilux Blue, Philips, Lumatek, Genesis, Ushio HiLux Gro MH Blue!

I dont have access to a multimeter now but Ill fix one.
So basicly some bulbs are more picky about their powersource and need very stable voltage output for the ignition phase.
My option are then as follow, keep 24/0, schedule on/off manually or get a new ballast/bulb?
Thanks for clearing things up for me