I've seen that before.
Basically, Trainz is busy saving your edits to your routes and sessions and your computer isn't refreshing the display at the same time causing the display to become white when you click on it. Unfortunately, you may have corrupted your route or session if you canceled the process because the file hasn't been completely written to disk. The larger the route, the longer this process takes. You are now going to have to run a DBR or an EDBR to clean up your database. Hopefully you have a backup of the route or session you had open when you exited the program.
You might want to try these:
1) Ensure you have enough disk space.
Programs such as Trainz swap stuff from memory to disk. This includes all kinds of temporary files, and other program data. If the disk space is low, then this process takes a lot longer to complete because the operating system is swapping around to fit the data.
2) When was the last time you defragmented your hard drive if it's a regular spinning disk?
Defragging your disks helps a lot with Trainz. The files are opened and closed and written constantly to disk. By defragmenting the disk, this speeds up the read/write process making the saving of files much faster.
3) If you are using an SSD, you definitely need to TRIM the drive. With Windows 10 and Windows 11, you can do this right through the built-in Defrag utility. Even though the program says defrag, it automatically switches to TRIM for SSD drives. TRIM doesn't help with speed but it ensures that your disk has marked empty cells for reuse.
4) You should run some disk diagnostics. A slow save or read can be a sign of a failing disk!
Check your hard drive for errors, and most importantly backup your data. This is very important with SSDs because when an SSD fails, it may lose performance initially but will fail suddenly with no recourse or ability to recover your data.
