What @david_2018 Is saying is that, once your sketch starts running, the Neopixel library will try to allocate 3 bytes of ram memory per led in your matrices, to hold the colour information of each led. That's 1.5K of the 2K ram memory available on Uno. It appears that @david_2018 compiled the code you posted and saw that it requires some ram for the sketch to use while running, leaving less than 1.5K left. When the sketch starts to run, there won't be enough to allocate the 1.5K needed, and all manner of strange things will happen, which could easily explain what you have seen.
I have a suggestion. Get an Arduino Pro Micro (not Pro Mini). This will be smaller and more convenient than Uno for a costume, has 2.5K ram, and an extra serial port you can use to connect to the BT module, while simultaneously using the USB port to help you debug your code using the serial monitor.