Have you tried adding a -log command-line argument to your packaged game .exe, and check if the server tick rate is set to 60hz?
How to create a command-line argument using Windows: Create a shortcut of the packaged .exe, right-click the shortcut and select properties, type " -log" (without the quotation marks) at the end of the Target input window.
You can search the command prompt log with ctrl+f and look for “tick”. It should display something like “(max tick rate 60)” when bringing up the level for play.