Is your IMXRT1050-EVKB has broken when you plugged LCD on J8?
Mine yes, because the capacitor C88 is rated only 6.3V. It's a bad design. The design should support at least 25V in this case. The Backlight dc/dc converter can boot the BL+ voltage up to 24V when open circuit or during normal operating.
Brief, you must change this capacitor for at least 25V, I suggest 35V in this case.