Hello,
the transition state search by default follows the mode which is closest to the initial transition vector. The statpt module calculates the overlap of the initial mode with those of each step and then follows the one which has the largest overlap.
First thing to check before running a transition state search after a frequency calculation is to make sure not having any approximate hessian files in your job directory - only the newly generated hessian file. So remove the file hessapprox if it is present in the job directory.
To always follow the mode with the lowest eigenvalue, try the keeptmode option in the $statpt section (see manual for details, search for keeptmode).
If the two lowest modes come get very close to each other, such that the overlaps of the initial eigenvector with both modes are similar, it might help to run a full Hessian calculation from time to time. An automated way can be activated by adding the hssfreq <number> keyword to $statpt, and the full Hessian will be calculated every N'th step. This can be very time consuming, though.
Good luck!
Uwe
