I'm using the last 1.15 version and the mod generate every 5 / 10 minutes this log :
�[mException in thread "Thread-1186" �[32m[12:25:11] [Thread-1186/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: java.lang.RuntimeException: Ruins crashed trying to access file .\world\RuinsPositionsFile.txt_writing �[m�[32m[12:25:11] [Thread-1186/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: at atomicstryker.ruins.common.RuinGenerator$FlushThread.doFlush(RuinGenerator.java:369) �[m�[32m[12:25:11] [Thread-1186/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: at atomicstryker.ruins.common.RuinGenerator$FlushThread.run(RuinGenerator.java:322) �[mException in thread "Thread-1189" �[32m[12:30:11] [Thread-1189/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: java.lang.RuntimeException: Ruins crashed trying to access file .\world\RuinsPositionsFile.txt_writing �[m�[32m[12:30:11] [Thread-1189/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: at atomicstryker.ruins.common.RuinGenerator$FlushThread.doFlush(RuinGenerator.java:369) �[m�[32m[12:30:11] [Thread-1189/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: at atomicstryker.ruins.common.RuinGenerator$FlushThread.run(RuinGenerator.java:322) �[mException in thread "Thread-1196" �[32m[12:40:11] [Thread-1196/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: java.lang.RuntimeException: Ruins crashed trying to access file .\world\RuinsPositionsFile.txt_writing �[m�[32m[12:40:11] [Thread-1196/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: at atomicstryker.ruins.common.RuinGenerator$FlushThread.doFlush(RuinGenerator.java:332) �[m�[32m[12:40:11] [Thread-1196/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:-1]: at atomicstryker.ruins.common.RuinGenerator$FlushThread.run(RuinGenerator.java:322)

I don't know why, but maybe something wrong in your generate code
Mod seems to work fine, so I don't know
The server doesn't crash, just generate this logs every 5 / 10 minutes
Hope it's helping

I can't reproduce the problem, but I took a crack at fixing it. Are you able to test it? You'll have to either build it yourself or wait for the next 1.15 Ruins release.