Has something happened to using pin18 as a UART rx? ESP32 generic

[davefes]

I have been running a UART on pin18 (rx) and pin19 (tx) for years
on a ESP32-SPIRAM variant. Decided to rationalise my ESP32 devices
so put a logging program on a ESP32 Generic (DevKitC) and the UART
didn't work. Changed devices and still no work. Then I changed to
pin22 (rx) and pin23 (tx) and it starts to receive data.

I only use the rx functionality. When my serial device is connected
to pin18 the high level drops from 3.3V to about 1.8Volts so I guess
it is not toggling the rx pin correctly. When I use pin22 for receive
the voltage stays up at 3.3V. pin18 as a rx pin seems to be loading
the serial drive more than when I use pin22

Nothing else is connected to pin18 or pin19. v1.26 generic build.

Any suggestions as to why it doesn't work?

Edit ... a loop-back test provided by AI passes on both pin setups.
Found on the esp32 forum;
There are three "power domains" on the chip, i.e. three separate power input sections.
Domain VDD3P3_CPU in on pin 37 (NOT GPIO 37) supplies power to GPIO5; GPIO18; GPIO23; GPIO19; GPIO22; GPIO3; GPIO1; and GPIO21.
This domain can SOURCE up to 40mA and SINK up to 28mA on STRENGTH 3

Do all these pins behave the same in input mode?