>No, it isn't pleasant.  We can't tell if it's a process problem
>(handling, baking, etc.) or a manufacturer defect in the parts.
>Since nobody knows why it's failing, we don't know where the
>flaw was introduced.

1. Did it used to work (i.e. is this a new batch of a previously produced 
product)?

2. If you take a unit that has the problem at room temp, and a unit that has 
the problem at a different temp, and swap crystals, which unit now has the 
problem at room temp?

My suspicion would be a subtle change in the way the crystals are 
processed - slight change in the angle of cut, that may be within the 
manufacturers tolerance, but causes your particular oscillator circuit 
problems. maybe you don't have quite enough gain at the desired overtone and 
too much at others.

With a 100MHz crystal you are gong to be operating at 5th or 7th overtone I 
would expect. Is the ferrite in the inductors from the same manufacturer as 
previously? A change in the loss curve here may be making the crystals shift 
between overtone modes due to ferrite loss dependence due to temperature. 

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