XF 1.5 Mass email is "hanging" and not completing

[Jme4200]

First of all, i have several websites running xenforo, and this is only happening on 1 of my websites, so my guess is this problem is server related.

It could also be because im running Xenforo v1.5.13

When i send a mass email, to 30k users, after a while it hangs on this screen

Screenshot

Captured with Lightshot

prnt.sc

Normally the number will hit 30k and notify me it's complete, however, the number is stick here. If i refresh the page, it asks if i want to resend the information, if i hit yes, the email starts sending again (starting from the number where it got stuck)

Is there a way to have this complete automatically without me having to refresh the page?

Many thanks

 

[Ozzy47]

Does it always stick at userid #13952?

 

[Jme4200]

no, stopped at 700, then 2000, then 13000

not these exact numbers, but approximately. it starts 5-10 minutes after i start sending the emails (but it might take my 5+ hours for the full 30k emails to send)