A 12AX7A is somehow enhanced from a 12AX7. In general a higher letter will work in an aplication designed for a lower letter but not always the other way. Unfortunately there is no standard for what the letters mean. It could be a higher voltage rating, a higher power rating, or just about anything. I wouldn't worry about it.
I wouldn't worry about the bias numbers on the new tubes.
Now to the arcing. I have worked on hundreds of tube amps and the vast majority of the time I've seen a tube arc it is the tube, not where it is placed in the amp (the socket.) Are you sure about this?? Is the arcing amp the one that blew the fuse?
If a particular tube flashes a bit when it warms up then that is probably OK as long it isn't arcing to the point that it is blowing fuses. If it really is true that any tube will flash when placed in a particular socket and doesn't in another socket then something is wrong with the amp. Some amps have circuits that ramp the voltages up slowly to avoid arcing. If that circuit is defective then I could see it arcing no matter what tube is installed.
I wouldn't worry about the bias numbers on the new tubes.
Now to the arcing. I have worked on hundreds of tube amps and the vast majority of the time I've seen a tube arc it is the tube, not where it is placed in the amp (the socket.) Are you sure about this?? Is the arcing amp the one that blew the fuse?
If a particular tube flashes a bit when it warms up then that is probably OK as long it isn't arcing to the point that it is blowing fuses. If it really is true that any tube will flash when placed in a particular socket and doesn't in another socket then something is wrong with the amp. Some amps have circuits that ramp the voltages up slowly to avoid arcing. If that circuit is defective then I could see it arcing no matter what tube is installed.