I think it will be easiest if you remove the syringe and fill it with methanol and the reinstall it. Please se the attached procedure on how to do this.
While running 5-10 purges of the sample syringe lightly tab the syring to get the air buble to move to the top so it can be flushed out. If this does not solve the problem loosen the syring while purging.
As a last resort remove the syringe, fill it with methanol , remove any air and attach it again and run the purge.
Many thanks Rune,
but can you please explain how to loosen the syringe.