Steps to reproduce

Example 1: Create an AnimationController like this:

controller = AnimationController(
        duration: const Duration(seconds: 2),
        vsync: this,
        lowerBound: 100,
        upperBound: 300);
controller.repeat();

Example 2: Create an AnimationController like this:

controller = AnimationController(
        duration: const Duration(seconds: 2),
        vsync: this,
        lowerBound: -100,
        upperBound: 200);
controller.repeat();

Expected results

The first animation starts with the value 100 and the second starts with the value -100.

Actual results

In the first example the animation starts with the value 200 and in the second example Flutter throws the following exception:

Assertion failed: file:///opt/flutter/packages/flutter/lib/src/animation/animation_controller.dart:889:12 _initialT >= 0.0 is not true

Code sample

Here is a DartPad that shows both issues: https://dartpad.dev/?id=79b890fd2a994d6e3f5ac210f433e7d5

Flutter Doctor output

Tested on the latest release and the latest main.