Period (full stop) being added randomly after words when typing

I am using a MacBook Pro 2017 running Mojave 10.14.6

Recently my MacBook has started adding a period after words while I'm typing.

It never used to do this.

I have read that a solution is to disable the "add period with double space" feature.

I'm reluctant to do this because I am not hitting the space bar twice, and I'd like to keep that handy feature.

Is this a known issue and is there a fix?