This is my first foray into the dark world of 9mm builds; I have a standard lower and a "filler block" that has to be either epoxied in place or the receiver itself drilled for a couple of screws, now that much really isn't an issue, what IS is the regular magazine lock is deep enough to go through the receiver and into the block, but not deep enough to engauge the 9mm double stack (Colt?) magazine.  
I've looked for ones with a thicker tab, and I suppose I could braze a piece on and machine it to fit, but before I do I figured it best to just ask.  

BTW: The Block isn't marked, so I've no idea who made it or where it came from: it all came to me a basket case.

I had to take a file to the flat surface in red. Fixed my problem using a Spike’s 9mm block. My symptoms were the same as yours. Attached File

I had a similar issue using converted Uzi mags.  I used a Rock River 9mm catch which protrudes about .02" deeper than a standard catch.  Part #9MM0099:  https://www.rockriverarms.com/index.cfm?fuseaction=category.display&category_ID=1731

any other place to buy this part from?

9mmar.com

Looks like they also sell the Spike's Tactical version:  http://9mmar.com/spikes-tactical-mag-catch-9mm-only/

I was going to send you to Brownells, but they are now discontinued.  Looks like Rock River is the only source.

The difference is they are thinner around the threaded post, allowing the catch to sink deeper into the lower.  File as shown above is another option.