OLTP to OLAP process causing deadlocks and impacting customers
Perhaps this problem has been solved meanwhile. Databases need dedicated knowledge and skills, any 10 year old kid can play around with SQL Server Management Studio, but creating and maintaining databases is not that easy. 

For SQL Server , make sure that Snapshot Isolation level is enabled. It's disabled by default, with the database in data locking mode, where long running queries block write acces, or even certain read accesses. I think Snapshot Isolation was introduced in SQL Server for analysis/OLAP.

Also, the OLTP tables should have proper indices. There should be somebody in the company knowing at least the basics of all this.