Shower grout failed

[Sipherlucian]

Hi folks, removing mouldy caulk from a shower and the grout was failing, little moist and crumbly in parts so i assume the water was running behind the caulk at those parts.

As im removing it theres what looks like a kind of fabric layer and a little bit of white caulk coming from the back of the grout being removed.
i assume the white caulk is the seal for the shower tray, then tiles overlaying that, would i be right? what could that fabric layer be, if it is a fabric layer? doubt its the tanking?

plan was to redo the grout and then re caulk but should i do anything else first just in case? thanks

 

[yorksbuilder]

Probably the edge of tanking tape. Dont dig any more out, and repair the grout and re-silicone, ensuring it fills the gap fully