Hi. Don't stepper motors stay locked in position when no signal is applied? Maybe not, that's what I'd understood. Would disabling the oscillator during the locking state help?
If you have one, maybe posting a schematic of your circuit might be helpful so other members can help trouble-shoot with you.
I vaguely recollect that the L298 is meant for quite small motors, I've only used one with 5V and approx. 50mA to 150mA stepper and DC motors. When I used to read about the L298 the term "gets hot quickly" appeared very often.