Javascript error after migration CRM 2016

Hey guys!

We migrated CRM 2016 last friday and now everytime we click on a contact we see this error message.

and

Here is also log files for both pictures above

1)

TypeError: Unable to get property 'children' of undefined or null reference
   at deleteActivitiesTab (ahcrm.hdsaas.com/.../ah_DeleteActivitiesTab)
   at eval code (eval code:1:1)
   at RunHandlerInternal (ahcrm.hdsaas.com/.../ClientApiWrapper.aspx)
   at RunHandlers (ahcrm.hdsaas.com/.../ClientApiWrapper.aspx)
   at OnScriptTagLoaded (ahcrm.hdsaas.com/.../ClientApiWrapper.aspx)
   at Anonymous function (ahcrm.hdsaas.com/.../ClientApiWrapper.aspx)

2)

TypeError: Unable to set property 'onclick' of undefined or null reference
   at filterAllActivities (ahcrm.hdsaas.com/.../ah_AllActivities)
   at eval code (eval code:1:1)
   at RunHandlerInternal (ahcrm.hdsaas.com/.../ClientApiWrapper.aspx)
   at RunHandlers (ahcrm.hdsaas.com/.../ClientApiWrapper.aspx)
   at OnScriptTagLoaded (ahcrm.hdsaas.com/.../ClientApiWrapper.aspx)
   at Anonymous function (ahcrm.hdsaas.com/.../ClientApiWrapper.aspx)

I checked - codes on both versions 2013 and 2016 are exactly the same