I use the Kodak version and it does fine. I would think the densities on the scale are okay and would be checking the timer accuracy against my watch. If that is good, remember the '1 stop' correction and continue to use the tool. The scales are great time/paper savers.

In time you may discover what has gone awry but, with the correction, it is still usable.

However, if you think it may be a warm up issue, try 6-10 second consecutive exposures and see if there is a difference.