I wanted to post this under the 0.43 bug, since the problem seems similar, but it's marked as fixed and locked. I had several bots that said they were building, but spent all night next to where they were supposed to be working. I have autosave turned off, and was trying to save and exit. Usually that fixes the problem. Instead, it looked like it was going to get stuck at "cleaning data" and eventually just gave me a white screen.
I'm posting this because I thought the JS stacktrace might possibly be helpful, and I'd like to help out. I'm running this on 64-bit Ubuntu (technically Linux Mint).
<--- Last few GCs --->
[15439:0x28cb069e1000] 207752593 ms: Mark-sweep 2032.7 (2214.2) -> 2032.6 (2167.7) MB, 1426.6 / 159.2 ms last resort
[15439:0x28cb069e1000] 207753843 ms: Mark-sweep 2032.6 (2167.7) -> 2032.6 (2152.7) MB, 1249.4 / 132.8 ms last resort
<--- JS stacktrace --->
==== JS stack trace =========================================
Security context: 0x1428b65a0bc9 <String[7]: file://>
1: push(this=0x9cc0dc02289 <JS Array[1454501]>)
2: Uint8ArrayConstructByIterable(aka Uint8ArrayConstructByIterable) [native typedarray.js:~201] [pc=0x6b0709be588](this=0x1a2aa7902311 <undefined>,Z=0x9cc0dc02201 <an Uint8Array with map 0xf8526ca73a9>,al=0x9cc0dc02421 <JS Array[1689041]>,am=0x12fc60204f49 <JS Function values (SharedFunctionInfo 0x1a2aa79500e9)>)
4: new constr...
Best bug report I've seen in a while. Of course it's from a Linux user. 😉
I too am getting a white screen every time it saves. It's been like that for a week already. There was a bug fix update through the App Store but it didn't fix this problem Unfortunately. I'm on an iPhone 6s.