I2C missing device

Dear all,
I am struggling with unreliable I2C behaviour.
When i take the NB-IoT shield and run I2C scanner, i get:

Scanning...
I2C device found at address 0x1D  !
I2C device found at address 0x1E  !
I2C device found at address 0x5D  !
I2C device found at address 0x5F  !
done

For the LSM303C (0x1D & 0x1E) i do not see the issue
The strange behaviour is for the LPS22HB (0x5D) and HTS221 (0x5F).

When i connect a LCD or OLED to the I2C bus.
I see the following output.

Scanning...
I2C device found at address 0x1D  !
I2C device found at address 0x1E  !
I2C device found at address 0x27  !
done

Scanning...
I2C device found at address 0x1D  !
I2C device found at address 0x1E  !
I2C device found at address 0x27  !
done

Scanning...
I2C device found at address 0x1D  !
I2C device found at address 0x1E  !
I2C device found at address 0x27  !
I2C device found at address 0x5F  !
done

Scanning...
I2C device found at address 0x1D  !
I2C device found at address 0x1E  !
I2C device found at address 0x27  !
done

You see that the 0x5F some time do respond, sometimes not at all.
The 0x5D does never responce when external I2C is connected.

Why?
What can i do to get external display to NOT interfere with the internal I2C device?

Which LCD or OLED device are you using? Can you provide a link?

I use something like this
and this
both same result.

The LCD 1602 device has the 0x27 address, The SSD1306 based device has a 0x3C address. Neither of which would appear to be in conflict with the other devices.

Can you test the voltage level of the IOREF 2.5E pin and then check the JP102 solder jumper:
http://support.sodaq.com/wp-content/uploads/2017/02/nb-iot_shield_rev3b_sch-1.pdf

You might need to add pull-up resistors for the external i2c devices (pulled up to the IO reference voltage of 3.3V or 5V).

I am currently on holiday in Denmark playing with the board. (No NB-IoT coverage here)
I did not bring additional pull-up resistors or Voltage meter, will try when I am back home.