ebike wattage working with rider wattage

[EbikeSLR]

Just purchased a Trek Domane+ SLR. When climbing, 5% plus grades, the my wattage may be 155 and the bike wattage, on occasion, may drop to 60 or less and the motor seems to lag making pedaling harder for a while. Is this normal? If so, what is going on? Thanks for the help.