Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 461.92
Broken: version: 2.93.0 Alpha, branch: master, commit date: 2021-03-27 14:01, hash: rBa9e7d503ddcd
Short description of error
Empty in provided .blend file cannot be moved on frame 1 when it has a keyframe on frame 1. It can be moved on any other frame with or without a keyframe on that frame, or on frame 1 if it doesn't have a keyframe.
Exact steps for others to reproduce the error
Select the Empty in the provided .blend file, and attempt to move it with g, transform sliders, etc. It will not move.
I'm not sure how I got my .blend file in this state, as my best effort at making a seemingly identical set of objects does not reproduce it. I'm guessing someone will have to inspect the internal state of these objects to find something amiss.