I went through a TOTAL door latch failure on my girls 98 civiv…was NOT fun to fix, nor easy. HOWEVER your car sound like your unlock rod or mechanism is binding. You can get to it from inside the car after you remove the door panel. A locksmith cannot help you if you have a latch failure like I did. The reason your latch snaps electrically back is because of rod binding… Try to overcome that physically with your finger on the unlock nub or by using the key… And be sure to keep the pressure on it in the unlock position while trying the handle.
My fix was a bit more drastic…I had to remove the inside conver remove the window and literally BASH the hell out of the latch until submission…my issue was caused by an internal fault in my latch…my mechanisms were working as was the unlock rod and handle…it was internal to my latch and there was no way past what I had to do.
TRY THIS…Use your key in the door and while turning it in the unlock position try the handle…lock and unlock it with the key sev times and try again…I think your lock rod isnt moving far enough to actually unlock your latch. If you are inside the car with the panel off try assisting the unlock rod while someone tries the handle. TRY EVERYTHING you can before you get to what I had to do… See what happens when you are applying pressure to the key in the unlock position while trying the handle. Let me know what you got and I can walk you thru more.