[Radioroslyn]

If you think it's a problem try few different osc tubes. Make sure all you or components around the osc are within tolerance. You may find that some will oscillate better than others. What sort of meter are you using the measure to grid voltage? I've found that digital meters may give an improper reading when used in an oscillator circuit. Best to use a VTVM (vacuum tube volt meter)or a fet volt meter. A vom will load the circuit so much that you won't get a good reading.
Food for thought
Terry