I have a 2003 honda civic with 86,000. When the car is cold and you drive off, it will slip only one time when the RPM gage is around 2. After that it does not slip anymore until the next day. The trans oil was changed around 15,000 miles ago however it was not the honda trans oil , I had the oil changed at a local shop
Have the mechanic make sure that the transmission oil level is up to the upper specification. A cold slip that goes away as the oil warms is an indication that the pump may be drawing air on that shift dipping the pressure. As the oil warms up, the volume expands and the level rises curing the problem.
If you have not already done so, have the recommended Honda trans oil put in. I know it costs more but Honda designed those transmissions, selected the bearings and frictions to run with their recommended oil. Don’t let ‘a local shop’ second guess Honda.