Why does CCES build every file when nothing has changed ?

We've built a small project based on the takthru example and when I rebuild the original, this doesn't happen, but in our project, it seems to rebuild every file every time we build. I've tried using VERBOSE=1 in the make command line but it still doesn't tell me why it's rebuilding everything. 

eg

18:08:43 **** Incremental Build of configuration Debug for project sharcfx_realtime_testing ****
make VERBOSE=1 all
'Building file: ../system/startup_lsp/lsp/mpu_table.c'
'Invoking: CrossCore SHARC-FX C Compiler'
ccfx -proc ADSP-SC835 -si-revision 0.0 -c -ffunction-sections -fdata-sections -mlongcalls -g -DCORE1 -D_DEBUG -DADI_DEBUG @includes-c4d225bfd7eae1e0d8dc5a8e9bdcb9b2.txt -MMD -MP -MF"system/startup_lsp/lsp/mpu_table.d" -MT"system/startup_lsp/lsp/mpu_table.o" -o "system/startup_lsp/lsp/mpu_table.o" "../system/startup_lsp/lsp/mpu_table.c"
'Finished building: ../system/startup_lsp/lsp/mpu_table.c'
' '
'Building file: ../system/sru/sru_config.c'
'Invoking: CrossCore SHARC-FX C Compiler'
ccfx -proc ADSP-SC835 -si-revision 0.0 -c -ffunction-sections -fdata-sections -mlongcalls -g -DCORE1 -D_DEBUG -DADI_DEBUG @includes-c4d225bfd7eae1e0d8dc5a8e9bdcb9b2.txt -MMD -MP -MF"system/sru/sru_config.d" -MT"system/sru/sru_config.o" -o "system/sru/sru_config.o" "../system/sru/sru_config.c"
'Finished building: ../system/sru/sru_config.c'

I seem to be randomly getting these "problem occurred" warnings pop up even on the example projects 

Doing a rebuild on the original talkthrough project as expected does..

18:13:28 **** Incremental Build of configuration Debug for project AD_TalkT_I2S_EZ_21835_Core1 ****
make all
make: Nothing to be done for 'all'.

18:13:28 Build Finished. 0 errors, 0 warnings. (took 127ms)

Any ideas ? 

Thanks