Harry Sewell

Yes deleting and redownloading minecraft resolved this issue for us

Deleting save data does fix it, I tried getting a realm to offload some worlds but due to  REALMS-8022 I cannot upload any worlds from switch. 

I've since been in a kafkaesque nightmare yoyoing between Mojang/Nintendo "support" trying to get a refund for my realms purchase.  

Neither of them take reponsbility and palm you off to the other entity. It is absolutley driving me round the bend. 

If you are thinking about getting a realm to save a few of your worlds before deleting your save data do not bother. 

I just purchased a realm and all uploads from switch fail.

As per https://bugs.mojang.com/browse/REALMS-8022

So not only does this bug cause hours of annoyance, I am  now out of pocket.

In order to try and solve MCPE-62708 (i.e delete all save data to stop minecraft taking 10+ minutes to load) I got a realm so my son could save three of his worlds and then fantastically ran into this bug. Unable to upload anything. My realms purchase is absolutely useless 

Minecraft ver 1.16.210
Switch ver 11.0.1
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My sons experience:

Profile has 2gb save data for Minecraft

1. Switch hard rebooted, Minecraft launched once switch stable

2. 03:48 of black screen

3. 08:58 of Red mojang screen

Settings/storage on his profile shows

35 worlds (455mb)

12 templates (381mb)

2 cached data items (233mb)

3 resource packs (148mb)

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My profile(I haven't played on this for about 6 months):

Profile has 1gb of save data for Minecraft.

1. Switch hard rebooted, Minecraft launched once switch stable

2. 00:02 of black screen

3. 00:14 of Red mojang screen

Settings/storage:

11 Templates (359mb)

25 worlds (292mb)

(Switch 11.0.1, Minecraft  1.16.100) My Son has 69 worlds, about twenty skin packs and 3 mash-ups!

Takes about 7 minutes with just a black screen after launching game and a further ten minutes on the Mojang red screen. 

My profile has two worlds and a couple of skin packs and launches in about 10 seconds. 

Now trying to go through his vast galaxy of worlds to see which ones aren't essential 🙂 

update — with now only 20 worlds it is performing much better, down to about 3 minutes to get into the menu screen. The save game data on the console is noted as 2GB which seems pretty  massive compared to other games on the console (e.g Breath of the wild, Minecraft dungeons, Mario kart and countless others < 80Mb).