What you’re experiencing is related to how sensitive the assessment is to setup and environment, and small variations can affect the results.
To improve consistency, please try the following:
Make sure the chest strap sits flat, snug, and level each time
Fully soak the ECG pads (5–10 seconds, rubbing water in well)
Keep your setup consistent (same time of day, similar conditions)
Lie still in a quiet environment during the assessment (no movement or talking)
It’s also important to take into account how you feel subjectively, and combine that with your results when making decisions. Using both objective data and your own perception will help you make the best choices for your training and recovery.
In general, it’s best not to rely on a single marker alone, but to look at the overall trend and context.