Rip error issues from prepress service agency

Hi,

I work in a small company which broker between clients worldwide and different printer/prepress services.

We receive artwork from a client, which we check for text errors and such, then pass it through to the prepress company for production. 

After receiving the prepress rip sample, we pass this along to the client for approval.

After the approval of the client we place the order for production, in this case over 100.000 items.

This goes well normally, but in this case the prepress rip returns following errors:

• 80 instances of spot colors used. (Our production order included the use of spot color)
• Hairline separation between 0,5 and 1 (I am trying to translate these technical terms from Dutch language)

After preflighting the clients artwork in acrobat, the report yields the same conclusion:

My question is should we:

1. Try fixing it ourself -
2. Let the prepress service fix it (more cost)
3. Send it back to the client for new artwork with fixed issues. 

Thanks for the upcoming advice(s)

CL