Newer marlin pushes the speed of the LCD as much as it can.
the BTT Graphics lcd is considerably slower than real RRD Graphics lcd's
Give this a try
In Marlin/src/lcd/dogm/ultralcd_DOGM.h
find U8GLIB_ST7920_128X64_RRD
and replace with U8GLIB_ST7920_128X64_4X_HAL
And set back to REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER
the BTT Graphics lcd is considerably slower than real RRD Graphics lcd's
Give this a try
In Marlin/src/lcd/dogm/ultralcd_DOGM.h
find U8GLIB_ST7920_128X64_RRD
and replace with U8GLIB_ST7920_128X64_4X_HAL
And set back to REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER