TypeScript error highlighting (performance)

Hi I have two Typescript projects. They are both quite small, but one is very small, about 15 TS/TSX files, and the other is about 50 TS/TSX files.

I see a big difference in the time it takes to highlight errors in the IDE, such as non-existent properties on a type. There is also a subtle difference in the output of the compiler, as seen below.

I have Typescript service enabled in settings. Both projects are using Typescript 2.0.10 (from node_modules). Both projects use identical tsconfig.json. Both have compileOnSave enabled. Both exclude node_modules.

Compiler output on slow project:

Process: Message 99 'ideCompile' server time, mills: 30
Process: Message 100 'ideChangeFiles' server time, mills: 0
Process: Message 101 'ideGetProjectErr' server time, mills: 1503

Compiler output on fast project:

Process: Message 182 'ideChangeFiles' server time, mills: 0
Process: Message 183 'ideCompletions' server time, mills: 16
Process: Message 184 'ideGetErr' server time, mills: 35

Notice that one says 'ideGetProjectErr' and the other says 'ideGetErr'...

IntelliJ IDEA 2016.3
Build #IU-163.7743.44, built on November 17, 2016

Any help much appreciated... while 1.5 seconds may not seem a lot, it does have a noticeable effect on productivity! Also it just seems strange that these two projects behave so differently.