Reproduction steps:

1. Open "MinimalRepro" project
2. "Tools" -> "Create MegaScript"
3. Wait for all the scripts to compile (Until the loading circle in the bottom right corner disappears)
4. Click on "File", "Edit" or any other toolbar selection

Expected Result: It opens immediately
Actual Result: After the compile, the menu opens with some lag

Reproduced with: 2018.1.0b3, 2017.3.0p2, 2017.2.1p2, 2017.1.3f1

Note:
The lag only occurs for the first time after the loading but comes back if the scripts recompile again
The lag mostly lasts for up to 2 seconds
After creating the scripts, reimporting them also reproduces the issue