Lens professionals: Focusing block?

Hey everyone,

Question on schematics of a lens: I just sent my 28-70mm F2.8 L USM lens in for repair and they called back saying that the focusing block was broken and needed to be replaced? They are doing it for free if they have a spare, but does anyone know what a focusing block is?

I'm sort of worried that this lens is going to start costing more than it's worth :/ Nearly $500 into it right now and I only value it around $600 or $700

I guess its the block of glass elements (group) which moves as you focus?

Whats exactly not working with the lens? Does it not focus?

I have heard spare parts for that lens are hard to come by and in some cases impossible without a dedicated trashed one to steal parts from. If they do have the part you need, consider yourself lucky.

Umm Occasionally if I zoomed out far enough (to "28mm" as it was marked) the lens would not function and the camera wouldn't take the picture until I zoomed in every so slightly. There were other issues as well with the lens lol

I realized that it's a difficult lens to find parts for without a donation lens to spare parts off of. I bought it for $190 with a delaminated lens element (pictures were still flawless) and I decided to send it in to tighten everything up and apparently they just opened it up (after 3 weeks -.- ) and that's what they've informed me of. If they have parts for it then I'll be ecstatic...if not then I'm probably SOL :/