When the OverflowMode of a Toolbar is set to ToolBarOverflowMode.None, changing a tool’s parameters programmatically can cause overflowed tools to disappear.
Reproduction example: https://blazorrepl.telerik.com/mzYKQEYM23bGXmvN56
In the meantime, a possible alternative is to use Adaptive="false" instead OverflowMode="ToolBarOverflowMode.None"