[CentOS] Bypassing 'A stop job is running' when rebooting CentOS 7

I'm currently trying to reboot a CentOS 7.5 workstation (to complete an 
upgrade to 7.6), but it is 'stuck' while shutting down with 'A stop job 
is running for ...' - the counter initially gave a limit of '1min 30s' - 
but each time it reaches that limit, it just adds on ~90 seconds to the 
limit ...

Currently the limit is '25min 33s'

I'm in no hurry to have this workstation operational, but I guess at 
some point I will have to power cycle it ...

Does anyone know how to bypass this? - or at least stop it increasing 
the limit each time it is reached?

It does seems rather pointless to keep increasing the limit like this ...

Thanks

James Pearson