Why sometimes Fiverr does not show which gig a client is contacting me from?

[jfsproduction]

I have few active gigs, some are the same but in different categories. 

For analytic purposes I like to see from which gig the clients contact me but recently some of the messages i receive don't show which gig they contact me from.

[jfsproduction]

I just realized i will get a quicker answer by asking to Fiverr support.

I will follow up with their answer in case someone is have the same problem.