Can you phosphate too much?

[acrmnsm]

We have a 4140M component that was phosphated after machining. It was subsequently reworked and then phosphated again.
Now in certain areas there are surface markings on the machined surface. See enclosed picture. Its like something has been leached out? Note the groove has been emery papered by the workshop which is why it looks a bit polished. Has this been caused by "too much" phosphating? Or something else?

 

[CoryPad]

Impossible to determine based on the current information and photograph.

 

[swall]

In the re-work and re-phosphating, was the phosphate stripped or was the phosphated piece put back through the process as-is?