Non-inverting op amp problem
Whenever you see a big difference between inverting and non-inverting terminals, one of three things may be happening:

- the open-loop gain is degenerate, so the error voltage cannot be reduced further
- the output is saturated, limited by the supply rails
- the measurement equipment was affecting the circuit


LM386 is an audio amplifier, not an op amp, even though it has some superficial similarity.

According to LM386 datasheet, the open-loop gain Av is only 26dB i.e. 20V/V. This is far from the ideal opamp where Av is considered near infinite.

Consequence of this reduced open-loop gain is that there will be significant difference between the inverting and non-inverting inputs, as you observed.