Hi,
(although ULN2003 has internal resistors but that is around 2.7K).
Yes, it is exactly what I meant. The problem not only is that MCU cannot sink the requested current, the problem also is that "loop-back" feature cannot detect logical One at pin and pFET3 is never opened. As result, pFET1 produces current within two oscillator periods only once at 0-to-1 transaction in the port latch; rest time it is only weak pFET2 which sinks very low current - it is not enough to open ULN transistors.

Good days!