Logstash restarts with "ConcurrentModificationException" error

I have an issue with logstash instances (There are 3 of them); they keep restarting after an hour or a while with this error (I have truncated the rest):

[2021-07-14T14:35:23,748][ERROR][org.logstash.execution.WorkerLoop][main] Exception in pipelineworker, the pipeline stopped processing new events, please check your filter configuration and restart Logstash.
java.util.ConcurrentModificationException: null
        at java.util.IdentityHashMap.forEach(IdentityHashMap.java:1358) ~[?:?]
        at org.logstash.Rubyfier.deepMap(Rubyfier.java:71) ~[logstash-core.jar:?]
        at org.logstash.Rubyfier.lambda$initConverters$8(Rubyfier.java:99) ~[logstash-core.jar:?]
        at org.logstash.Rubyfier.deep(Rubyfier.java:53) ~[logstash-core.jar:?]
        at org.logstash.ext.JrubyEventExtLibrary$RubyEvent.ruby_get_field(JrubyEventExtLibrary.java:85) ~[logstash-core.jar:?]
        at usr.share.logstash.vendor.bundle.jruby.$2_dot_5_dot_0.gems.logstash_minus_filter_minus_ip2location_minus_2_dot_1_dot_0.lib.logstash.filters.ip2location.RUBY$method$filter$0(/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-filter-ip2location-2.1.0/lib/logstash/filters/ip2location.rb:50) ~[?:?]
        at org.jruby.internal.runtime.methods.CompiledIRMethod.call(CompiledIRMethod.java:117) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.internal.runtime.methods.MixedModeIRMethod.call(MixedModeIRMethod.java:156) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.ir.targets.InvokeSite.fail(InvokeSite.java:253) ~[jruby-complete-9.2.8.0.jar:?]
        at usr.share.logstash.logstash_minus_core.lib.logstash.filters.base.RUBY$method$do_filter$0(/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb:143) ~[?:?]
        at org.jruby.internal.runtime.methods.CompiledIRMethod.call(CompiledIRMethod.java:117) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.internal.runtime.methods.MixedModeIRMethod.call(MixedModeIRMethod.java:156) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.ir.targets.InvokeSite.fail(InvokeSite.java:253) ~[jruby-complete-9.2.8.0.jar:?]
        at usr.share.logstash.logstash_minus_core.lib.logstash.filters.base.RUBY$block$multi_filter$1(/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb:162) ~[?:?]
        at org.jruby.runtime.CompiledIRBlockBody.yieldDirect(CompiledIRBlockBody.java:146) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.runtime.BlockBody.yield(BlockBody.java:114) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.runtime.Block.yield(Block.java:170) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.RubyArray.each(RubyArray.java:1800) ~[jruby-complete-9.2.8.0.jar:?]
        at usr.share.logstash.logstash_minus_core.lib.logstash.filters.base.RUBY$method$multi_filter$0(/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb:159) ~[?:?]
at org.jruby.internal.runtime.methods.CompiledIRMethod.call(CompiledIRMethod.java:117) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.internal.runtime.methods.MixedModeIRMethod.call(MixedModeIRMethod.java:156) ~[jruby-complete-9.2.8.0.jar:?]
        at org.jruby.internal.runtime.methods.DynamicMethod.call(DynamicMethod.java:200) ~[jruby-complete-9.2.8.0.jar:?]
        at org.logstash.config.ir.compiler.FilterDelegatorExt.doMultiFilter(FilterDelegatorExt.java:99) ~[logstash-core.jar:?]
        at org.logstash.config.ir.compiler.AbstractFilterDelegatorExt.multiFilter(AbstractFilterDelegatorExt.java:115) ~[logstash-core.jar:?]
        at org.logstash.generated.CompiledDataset158.compute(Unknown Source) ~[?:?]

Here's the FATAL error and logstash instances shut down after this:

[2021-07-14T14:35:23,972][FATAL][logstash.runner          ] **An unexpected error occurred! {:error=>java.lang.IllegalStateException: java.util.ConcurrentModificationException,** :backtrace=>["org.logstash.execution.WorkerLoop.run(org/logstash/execution/WorkerLoop.java:85)", "jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)", "jdk.internal.reflect.NativeMethodAccessorImpl.invoke(jdk/internal/reflect/NativeMethodAccessorImpl.java:62)", "jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(jdk/internal/reflect/DelegatingMethodAccessorImpl.java:43)", "java.lang.reflect.Method.invoke(java/lang/reflect/Method.java:566)", "org.jruby.javasupport.JavaMethod.invokeDirectWithExceptionHandling(org/jruby/javasupport/JavaMethod.java:440)", "org.jruby.javasupport.JavaMethod.invokeDirect(org/jruby/javasupport/JavaMethod.java:304)", "usr.share.logstash.logstash_minus_core.lib.logstash.java_pipeline.start_workers(/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:243)", "org.jruby.RubyProc.call(org/jruby/RubyProc.java:295)", "org.jruby.RubyProc.call(org/jruby/RubyProc.java:274)", "org.jruby.RubyProc.call(org/jruby/RubyProc.java:270)", "java.lang.Thread.run(java/lang/Thread.java:834)"]}

The Nginx logs changed and a part was added to it; therefore, I changed grok patterns and add that field in the filter pattern as well. After that, logstash instances kept restarting but they parse logs and ship them to elasticsearch and I can see the structured data on the Kibana dashboard as well (they use cache). Can anyone help me with this? Thanks in advance.