Openstack refres stoppped working

Hi, our MIQ instance is unable for the last few days to read new VM instances or tenants from our company openstack provider. evm.log is filled with error from refresher job:

[----] E, [2020-11-20T10:48:09.800307 #10278:4da5f8] ERROR – : MIQ(ManageIQ::Providers::Openstack::CloudManager::Refresher#refresh) EMS: [openstack.kb.cz], id: [7] Unable to perform refresh for the following targets:
[----] E, [2020-11-20T10:48:09.800382 #10278:4da5f8] ERROR – : MIQ(ManageIQ::Providers::Openstack::CloudManager::Refresher#refresh) — ManageIQ::Providers::Openstack::CloudManager [openstack.kb.cz] id [7]
[----] I, [2020-11-20T10:48:09.875858 #10278:4da5f8] INFO – : MIQ(ManageIQ::Providers::Openstack::CloudManager::Refresher#refresh) Refreshing all targets…Complete
[----] E, [2020-11-20T10:48:09.876152 #10278:4da5f8] ERROR – : MIQ(MiqQueue#deliver) Message id: [97700615], Error: [no implicit conversion of nil into String]
[----] E, [2020-11-20T10:48:09.876275 #10278:4da5f8] ERROR – : [ManageIQ::Providers::BaseManager::Refresher::PartialRefreshError]: no implicit conversion of nil into String Method:[block (2 levels) in class:LogProxy]
[----] E, [2020-11-20T10:48:09.876368 #10278:4da5f8] ERROR – : /var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:67:in refresh' /var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:11:in refresh’
/var/www/miq/vmdb/app/models/ems_refresh.rb:103:in block in refresh' /var/www/miq/vmdb/app/models/ems_refresh.rb:102:in each’
/var/www/miq/vmdb/app/models/ems_refresh.rb:102:in refresh' /var/www/miq/vmdb/app/models/miq_queue.rb:479:in block in dispatch_method’
/usr/local/lib/ruby/2.5.0/timeout.rb:93:in block in timeout' /usr/local/lib/ruby/2.5.0/timeout.rb:33:in block in catch’
/usr/local/lib/ruby/2.5.0/timeout.rb:33:in catch' /usr/local/lib/ruby/2.5.0/timeout.rb:33:in catch’
/usr/local/lib/ruby/2.5.0/timeout.rb:108:in timeout' /var/www/miq/vmdb/app/models/miq_queue.rb:477:in dispatch_method’
/var/www/miq/vmdb/app/models/miq_queue.rb:454:in block in deliver' /var/www/miq/vmdb/app/models/user.rb:290:in with_user_group’
/var/www/miq/vmdb/app/models/miq_queue.rb:454:in deliver' /var/www/miq/vmdb/app/models/miq_queue_worker_base/runner.rb:104:in deliver_queue_message’

I have no idea where to look. Fog.log doesn’t help and from that stacktrace I am not even sure if it is about openstack API problem or something local on MIQ cluster.
I have also found a similar trace here https://access.redhat.com/solutions/5295101 - but I can’t view details (not having redhat account)

Could anyone point me to the right direction please?
Thank you