Weird, Google apps work correctly here. Does it work fine in xiaomi eu rom correctly?
For the flashing procedure, ROM zip contains all the images including boot and vendor_boot, you can use an older boot image to flash the ROM zip if newer one doesn't work for you. Since boot and vendor_boot are included in the ROM itself, they get flashed while flashing the ROM (so you always end up with the latest available version). So, your flashing procedure is fine too.
The stock MIUI rom worked just fine in this regard.
I'm doubtful of it being a potential rom issue. If it were i'd expect either no camera function to work or a range of specific functions not working (like no video or no audio). This doesn't seem to be the case as the camera core function (photo/video) work just fine. It's the timelapse specifically that doesn't work.
Does it work for you? I'm assuming, since you reply in this thread, that you have the same phone and same rom running but can use the timelapse in all it's glory?