Transistor differential wein bridge oscillator wrong frequency
The diffpair is running at 12+mA. Rin (at the base) is about 400 ohms.

I doubt the coupling capacitors are sized for that low an impedance.

Also the 250 Ohm biases your transistors with very low Vce, so I'd increase that to 510 ohms (you can buy a 510 ohm).

Alter the circuit to be like this







simulate this circuit &ndash; Schematic created using CircuitLab

Rin will be approximately 500,000 ohms, up from 400 ohms.

Instead of "linear" range of diffpair being about +- 0.03 volts, this use of emitter-linearization (aka emitter degeneration, of the gain) provides +- Itail * Rem = +-0.5 volts. 

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Added the 5th bipolar, to reduce Rout from 1Kohm to about 3 ohms. Rout is 1/gm or 1/(0.009/.026). The pulldown is still only 1K ohm. The pullup is very strong.

For moderate amplitudes, this circuit should give you VERY LOW distortion. The challenge is how to control the amplitude; you will need some nonlinearity, perhaps a series D+R across the negative feedback (actually back-to-back diodes, in series with a resistor that softens the nonlinearity)