Hi Bikasgurung,
I’m experiencing the same issue with the “connection lost” error in WordPress. Interestingly enough, I’m running 4.4, and haven’t updated to 4.5 as of yet.
I was initially curious that 4.4 was my issue, but if you say 4.4 was running smoothly, I’m wondering if something else is the cause.
Who is your host? I’m running an Amazon AWS hosting service.