When I broke an adjacent block next to a lava source block. the lava didn't update and didn't flow, the lava just stood still and didn't flow. I tested this multiple times and the same thing happened. When I mined around the source I noticed it was only 1 source block exposed next to a mineshaft, which may be a factor. I tried searching if others have reported this bug but could only find related bug reports, nothing such like this.