any ideas why UART might be eating my bytes? that's supposed to be counting up

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Hello DM10!                                                                      
Hello 111!                                                                       
Helllo DMA World d 2114!                                                         
World 2118!MA World 21121!                                                       
Hello2122!                                                                       
Hell 2123!                                                                       
Hed 2124!                                                                        
Hello DMA World 2125!                                                            
Hello DMA World 2126!                                                            
131!o DMA World 2127!                                                            
Helloo DMA Worldorld 2137!                                                       
Hello DMA World 2139!                                                            
Hello D DMA World 2142!                                                          
Hello DMA World 2143!                                                            
Hello DMA World 2144!