Frequency Offsets Computed By GnuRadio code - ofdm_sync_pn.y

Hello,

The frequency offset computed by ofdm_sync_pn.py turns out to be a
different value every time I transmit a packet.

Frequency offsets vary in longer timescales but I get completely
non-correlated values every time I make transmissions between a
transmitter-receiver pair.

When I sent back-to-back packets, the offset estimation from different
preambles deviate as big as 30-40%. Is this the expected behavior? Will
appreciate if somebody can help me figure out whats going on here?

Thanks,
M