Do you have latest version of the game?
I mention the Shuu route specifically because I haven't seen this pop up with either the Shiba or Toru routes.
But basically on Fridays if I click on the text message button specifically and then click to exit out of them, the screen will either go black or it'll pull up the background CG for the office. There are no options to click out of what I'm seeing so it essentially freezes the game until you close the program (the message before closing pops up and works like normal). So far from trying to replicate it I haven't encountered any issues anywhere except in the Commercial District. It occasionally happens when looking at the the Commercial District as a whole, but it's happens almost every time when you go into any of the buildings in the Commercial District, pull up, and then exit out of the text messages.
Let me know if this was clear. If you want to see what's happening I'd be happy to record and send a video of what's going on (I can post that on here or send that privately)