I’ve had that happen both inside and outside. Here are some poorly controlled 1-min jobbers done outside last week:
Now that is some oscillation! #strugcity that day 
However it doesn’t usually happen when:
- I’m actively working to pedal smoothly and in circles (vs ‘kicking’ over the top)
- I don’t over-power the start of interval
Some examples of good intervals both inside and outside:
Kickr 2017 (wheel off) on Bashful -3 using PowerMatch with Stages crank power meter:
That was in Erg mode and big chainring which shows more realistic power deviations, as compared to outside.
Closeup of the first one (in 2nd set) with some statistical data:
Now I’m going to compare that inside 1-min interval to a similar interval done outside:
Absolutely no concerns on either inside or outside.