The usual culprits of this are:
1) Antivirus is stomping on the data as you open up the content in Surveyor. This can cause all kinds of performance problems overall including while driving.
Exclude your data folder from real-time Antivirus scanning and this will help a lot.
2) The data is being precached and indexed.
This process occurs when new content is downloaded or there's been an update. You'll see precaching something. The something is various assets, scripts, images, etc., that are being referenced in the database.
To find this out, click on the triple-bars in the upper left corner to bring up the Main Menu then Click on show Launcher. Once the Launcher is shown on the screen, click on Developer and then Show Logs.
The logs will show stuff scrolling down the screen with various messages about validating content, loading content, etc. There's not much you can do until this finishes the process. There is a way to make this go faster and that requires enabling the advanced debugging tools in the Trainz settings under the Dev tab. Then running Trainz Util from the Developer menu. In the Trainz Util window, put in prebuild.
To speed up the loading and caching, I highly recommend defragmenting your hard disk(s) if these are not SSD drives. A defrag operation is disabled on SSDs and only a TRIM operation will occur anyway.
