I can replicate this too. Here is a quick video showing the issue. I managed to duplicate 4 shops before it gave an error. Then deleting any one of the shops removes them all. Each shop will bring up the same window and not a new window for each shop.
EDIT: Game Version: V0.3.4.1(,debug) (linux x86-64)
Operating System - windows 10,64-bit
OpenRCT2, v0.3.4.1 (eba2041 on develop)
I encounter a bug when rebuilding/relocateing a stall/shop. The stall/shop cannot be demolished in the first step and I can only choose a new location to build the stall. However the original shop stays. Therefore 2 identical shops are built. When I demolish the new shop, the old shop is also demolished.
You could find the saved file, as well as the screenshots in sequenece below. Thank you!
Six Flags shop bug.sv6