MC-179858 is still not fixed. I just tried making a new map, and it still showed those horrid grey static corruption lines. Please, don't list an issue as resolved unless it is actually fixed.
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Did you ever open the affected world in 20w17a? Or is it a newly generated one, or one that was last opened in 1.15.2?

Yes, I downloaded the 20w17a snapshot on Monday, yesterday I went to update the location of one of my banner markers, and the map went haywire. I tried both using pick block on the map, which was in an item frame on a table in my house, and making a new one, both came out wonky. Today, I went and downloaded the 20w18a snapshot and booted up the world. I had last exited on my map table, holding the newly created map in my hand, and the older pick block map over near the center of my hot-bar, not in my hand. I had expected either the new map or the old pick block one to update, neither did. I deleted the pick block map and the newly created one, and then pick blocked the same map again, nothing changed, I tried creating yet another new map, it looked the same as the one I created in 20w17a. So, yeah, there's my issue. I would try pick-blocking another map, but I don't want any more damage to my map table, which is also my dining room table, in front of my fireplace, in-between the stairs going to the second floor, and being the first thing seen when entering the front door.

This comment is from report# MC-179858
Dear, Bartosz Bok (Assignee),
@unknown (Last dev who responded), and whom else it may concern,
This is still a major Bug in Snapshot 20w18a, as shown in the pictures I just added to this report.
When player walks/ flies around to update their map(s), this Bug occurs.
My system/version is MC Java Snapshot 20w18a Windows 10 version 1909.
Please Have this Bug Re-Opened and maybe check it more thoroughly during that time. I'm not trying to be rude when I say that, its just that in my 3.5 years (and counting) of playing Minecraft, I've seen Bugs get fixed and thought to be long gone, resurface after a long time, or they somehow get added to new updates. I am not at all saying that you moderators and developers are bad, y'all are excellent at what you do. That's the truth. The fact is: No One Is Perfect (Except our Lord God Almighty ( If you believe in Him. No Offense if you don't.)) and it's just our nature for things like this to creep in sometimes.
Thank y'all for all that you do,
JAG

This comment is from report# MC-179858
Dear, Bartosz Bok (Assignee),
@unknown (Last dev who responded), and whom else it may concern,
This is still a major Bug in Snapshot 20w18a, as shown in the pictures I just added to this report.
When player walks/ flies around to update their map(s), this Bug occurs.
My system/version is MC Java Snapshot 20w18a Windows 10 version 1909.
Please Have this Bug Re-Opened and maybe check it more thoroughly during that time. I'm not trying to be rude when I say that, its just that in my 3.5 years (and counting) of playing Minecraft, I've seen Bugs get fixed and thought to be long gone, resurface after a long time, or they somehow get added to new updates. I am not at all saying that you moderators and developers are bad, y'all are excellent at what you do. That's the truth. The fact is: No One Is Perfect (Except our Lord God Almighty ( If you believe in Him. No Offense if you don't.)) and it's just our nature for things like this to creep in sometimes.
Thank y'all for all that you do,
JAG
Please follow the instructions from MC-179858.
Please follow the instructions from MC-179858.
Also I'm not a dev.
Also I'm not a dev.

Good news, my map is fixed. YAY! However, I now have another problem, not really a bug, just a problem. Somebody stole a pair of Blackstone Anchors off my Trade Galleon, and my Ender War Galleon. I had to swim out there to retrieve them after they floated off, as both somehow, without a captain driving them, managed to avoid my stone mines surrounding my private port. Now I'm nestled by the fireplace in my private study, my favorite red dyed leather armor pajamas are in the wash, I just realized I don't have a washing machine to wash them in my house, my butt's cold, and I had to dive down and chain my ships to a submerged fence post, like a lead on a cow, so they wouldn't float off again. Oh well, at least my map is fixed. I'm gonna go eat a baked potato, see you later.... Good Job on fixing the maps. Thanks. Rockatoa, a wishing I had a heated bath in my house Brickticks out) not found.
Did you ever open the affected world in 20w17a? Or is it a newly generated one, or one that was last opened in 1.15.2?